Pajtim Kasami fired the hosts ahead in the first half with a low finish from the edge of the box.
Find out how the action unfolded below.
6.45pmGood evening everyone! It has already been a record breaking week of Champions League football, with 40 goals scored across last night's eight games. Many will be hoping that Olympiacos and Juventus are just two of the sides to keep up the trend today.
6.48pmAfter such a good start to their group stage campaign, it all went wrong for Olympiacos last time out. They had been expected to record three points against Malmo, but poor defending cost them dearly as they went down 2-0 in Sweden.
6.51pmIt wasn't a great night either for Juventus as they fell to a 1-0 defeat against Atletico Madrid. Arda Turan's late winner was all that separated the teams in Spain and it ensured that each club in Group A finished the night level on three points.
6.54pmOLYMPIACOS XI: Roberto, Maniatis, Botia, Elabdellaoui, Abidal, Masuaku, Milivojevic, N'Dinga, Dominguez, Kasami, Mitroglu
6.55pmJUVENTUS XI: Buffon, Ogbonna, Bonucci, Chiellini, Lichtsteiner, Vidal, Pirlo, Pogba, Asamoah, Morata, Tevez
6.56pmOLYMPIACOS SUBS: Megyeri, Giannoulis, Avlonitis, Afellay, Durmaz, Fuster, Diamantakos
6.57pmJUVENTUS SUBS: Storari, Evra, Pereyra, Marchisio, Llorente, Giovinco, Coman
7.00pmKostas Mitroglou leads the Olympiacos attack this evening, having scored twice for his club at the weekend. Pajtim Kasami and Alejandro Dominguez will be the two players tasked with providing him with support. There is also plenty of experience in the back four in the shape of former Barcelona man Eric Abidal.
7.03pmAs for Juventus, there is a return to the starting lineup for Arturo Vidal. Kwadwo Asamoah and Alvaro Morata are the two other players who come into the team this evening. Andrea Pirlo, Paul Pogba and Carlos Tevez also start in a near full-strength XI for the Bianconeri.
7.06pmOlympiacos will have felt that they were handed a tough group when the draw was first made for this season's Champions League. It was always going to be a tough ask against the champions of Italy and Spain, but they made the perfect start by beating Atletico 3-2 on the opening matchday.
7.09pmPicking up three points away to Malmo in their next match seemed like a certainty, but they just did not find their form and suffered a shock 2-0 defeat. Marcus Rosenberg scored both goals that evening for the Swedes, as the Greek side's defence fell apart.
7.12pmThat loss meant they went into the international break off the back off two defeats, but they returned to winning ways with a 3-2 win over Ergatolis at the weekend. That result left them third in the league, trailing leaders PAOK by three points.
7.15pmIf tonight's match is meant to be big for the club, then words can hardly describe the size of Sunday's clash against city rivals Panathinaikos. It always a feisty affair when they go head to head and that is no surprise given that they are the most successful teams in Greek history.
7.18pmAlso hoping to get their tournament back on track is Juventus. The three-time Italian champions started off with a comfortable 2-0 win at home against Malmo, with Carlos Tevez finding the net twice in Turin.
7.21pmHowever, they lost away to last season's finalists Atletico, in what many expected to be their toughest match in the group. It still seems that there is a long way to go for them to transform their domestic form into European glory.
7.24pmThat defeat in Spain is the club's only reverse of the season so far. They are currently top of the Serie A table, having won six of their opening seven games and they dropped points for the first time at the weekend in a 1-1 draw with Sassuolo.
7.27pmThese two teams have met eight times previously. In those matches it is Juventus who have come out on top more often, having won five times and suffered just one defeat. Olympiacos' sole success was a 2-1 win in Italy during a UEFA Cup tie in 1999, but they lost at home to go out 4-3 on aggregate.
7.30pmOlympiacos will not need reminding what happened the last time that they faced Juventus. In a group stage match back in 2003 the Old Lady recorded a 7-0 win over the Greeks. David Trezeguet and Alessandro Del Piero were among the scorers that evening.
7.33pmA stat that will give confidence to the Olympiacos fans this evening, is that the club have won their last four Champions League games at home. Last season they beat Benfica, Anderlecht and Manchester United and of course kicked off this campaign with a win over Atletico.
7.36pmIt really is all to play for in Group A at the moment. A quick look at the table shows all four teams with three points after their first two matches. Juventus actually lead the way on goal difference, while Olympiacos are bottom, but of course it is too early to make anything of that.
7.39pmPREDICTION: This is a tough one to call and I expect it to be a very tight match. Olympiacos will have to defend better than they did against Malmo as Juve could really punish them with their quality. I have a feeling that the visitors will sneak a win, with 2-1 to Massimo Allegri's men how I see it finishing.
7.42pmBoth sets of players are out on the pitch and lined up as the Champions League anthem roars out. We are now just three minutes away from the start of the match in Athens!
1 minKICKOFF! We are underway at the Karaiskakis Stadium!
2 minOlympiacos have started this match well and they create a good chance when Kasami works some room down the left and whips in a cross to the front post looking for Mitroglou. However, Chiellini got there just in time to clear the danger as the striker looked to add the finishing touch.
5 minCHANCE! It really has been a bright start by the hosts and they are looking a threat down the left. This time it's Masuaku who breaks clear and he drills in a low cross that Mitroglou connects with, but he can only fire his strike wide of the target.
7 minSAVE! Olympiacos are given a great opportunity as they win a free kick around 25 yards out from goal in a central position. Dominguez steps up to take it and his curling effort looks headed for the top corner before Buffon gets a hand to the ball to tip it over the bar.
10 minJuventus are just starting to see a bit more of the ball after such a good start by the home side. The Greek fans are in full voice across the ground and it must be such an intimidating atmosphere for the opposition to play in.
11 minThe visitors show their first real glimpse of an attacking threat as Morata bursts clear down the right. He turns his defender inside out and drills in a low ball looking for Tevez, but the hosts manage to put the ball behind for a corner.
12 minOFF THE LINE! From the resulting set piece Juve almost take the lead, as the corner is whipped into the middle by Pirlo and ends up dropping kindly to Tevez. He can't get clean contact on the ball and looks to guide it into the net, but Elabdellaoui was there to head the ball off the line.
13 minThe pace of this game is relentless at the moment and this time it's Olympiacos' turn to attack. They lead a break with Milivojevic eventually receiving the ball and finding space to get a shot away. His long-range effort doesn't look the most dangerous of hits, but it requires Buffon to just help the ball over the bar.
16 minAlthough we haven't seen any goals as yet, this game has been great to watch. Both teams are sensing the chance to have a real go at their opponents and commit plenty of men forward to each attack.
19 minGOAL DISALLOWED! Juventus are looking extremely dangerous from corners and it's Tevez again who is the main threat. Following another scramble, Chiellini manages to flick the ball to Tevez at the back post, who then heads into the net, but as he was standing behind the keeper the goal is correctly ruled out.
23 minOlympiacos seem as if they are keen to try their luck from range this evening and Kasami picks the ball up in space and fancies his chances. His low drive is well hit, but it is pretty central and it would take something of outstanding quality to beat a world-class goalkeeper such as Buffon.
26 minYou just feel that Juventus could find another gear at any moment and when they break at pace they look a real threat. On their latest attack a flowing move almost comes to fruition as Tevez tries to thread the ball through to Vidal, but his final pass is just too long and runs through to the keeper.
27 minCHANCE! This really would have been a stunning goal had it found the net. Masuaku plays a low ball to the front post that is brilliantly controlled by Dominguez. The ball then sits up perfectly for the Argentine and he fires in a strike on the volley, but his effort flashes just wide of the far post. Great play all around from the hosts.
30 minWe still haven't seen any bookings so far, but Milivojevic is very lucky to avoid a yellow card for a high challenge on Vidal that almost catches the Chilean on the head. Aside from that, this match has been played in the right spirit, with the football doing the talking so far.
33 minThe game has just become slightly scrappy in the centre of the midfield with both teams unable to put together a spell of possession. Juventus are also taking a few risks with some dangerous looking passes around their backline and Pogba is lucky that an under-hit ball is cleared by his dfence before the hosts can profit.
35 minGOAL! Olympiacos 1-0 Juventus (Pajtim Kasami)
35 minThe roof has just been raised as the home side take the lead with 10 minutes of the first half remaining. Juventus lose the ball cheaply inside their own half and Mitroglou is played free down the left. He then looks up and spots Kasami on the edge of the box and the Swiss international makes no mistake with a fine low finish into the bottom corner.
37 minYELLOW CARD! Lichtsteiner is the first player to pick up a booking for a foul on Masuaku by the left-hand touchline. It gives Olympaicos a free kick in a promising position, but the delivery fails to beat the first man.
40 minJuventus try to muster up a quick response and they commit plenty of men forward in search of a goal. The ball eventually breaks to Vidal just outside the box, but his low effort is drilled straight at Tevez as the move breaks down.
43 minCHANCE! What a chance for Juventus to draw level before the break. They win a free kick on the left that Pirlo plays into the box. The ball is then flicked goalwards by Chiellini, but none of his teammates can scramble the ball into the net and the hosts somehow get it clear.
44 minYELLOW CARD! Juventus win another free kick as Botia fouls Morata just outside the box. The Olympiacos defender is booked and it has given the visitors a great chance from the set piece.
45 minCHANCE! Of course it was Pirlo who took the set piece and instead of trying to find any of his teammates he goes for goal with a powerful strike that heads just over the bar.
45 minThere are going to be two minutes added on at the end of the first half.
45+2 minHALF-TIME: Olympiacos 1-0 Juventus
8.34pmThe referee brings an end to the first 45 minutes and it's Olympiacos who are in the lead. Kasami's strike has put the Greek champions deservedly in front after a very watchable half and as things stand they are on top of Group A.
8.38pmThe statistics show that there has not been much between the two teams this evening. Juventus are actually shading possession, having seen 53% of the ball. Olympiacos have had more shots on goal, with seven compared to six from the visitors. However, Juve have only hit the target once and Allegri will want to see more from his forwards after the break.
8.42pmA quick look around the rest of the matches in Europe this evening shows that there haven't been too many goals. Aside from Real Madrid leading Liverpool 3-0 and Dortmund beating Galatasaray by the same scoreline, it is goalless in every other fixture.
8.46pmIf Allegri wants to make some changes for the second half then he has plenty of options on the bench. Fernando Llorente hasn't found the net this season, but he can prove to be a handful on his day. Sebastian Giovinco is another that can provide a real spark to the attack and he impressed as a sub during Italy's recent wins over Azerbaijan and Malta.
46 minJuventus take the kick off and get us back underway in Athens!
48 minThe visitors have started the second half well and have seen a lot of the ball in these early stages. They then manage to win a corner after a good piece of play by Bonucci, but they are unable to make the set piece count.
51 minCHANCE! Another good move by the visitors sees Pogba pick out Morata inside the box. The Spaniard then tries to guide the ball into the far corner on the volley, but his attempt heads a couple of inches wide of the target.
54 minPirlo hasn't quite found his usual range of passing this evening and another of his long-balls looking for Asamoah is cut out by the Olympaicos backline. His deliveries from set pieces hasn't been great either and his side will be hoping that his undoubted class can shine through in the remaining minutes of this half.
56 minYELLOW CARD! N'Dinga is the second Olympiacos player to pick up a booking. He had given away a free kick for a high challenge on Vidal, but appeared to be cautioned for his complaints to the referee.
57 minThis latest free kick just sums up Pirlo's night. The midfielder goes for goal from around 30 yards out, but his effort is poor and it swings well wide of the target.
57 minSUBSTITUTION: That's the last contribution that Pirlo will make this evening, as on his 99th appearance in the Champions League he is replaced by Marchisio.
59 minYELLOW CARD! The referee hands out another booking and it's Pogba who picks up the card this time for catching Botia as the two challenged for the ball.
60 minCHANCE! Olympiacos really should be 2-0 up as Kasami is picked out inside the box by Dominguez, but he ends up side-footing his effort inches wide of the far post. That could prove to be a huge moment in this match and Juventus are lucky to still be just a goal down.
63 minJuventus have only shown brief glimpses of their quality this evening and they have still only had one shot on target. Tevez seems to be their most likely goalscorer, but after being picked out in the box and working some room to shoot, he ends up bending a shot wide of the post.
65 minSAVE! The visitors are so close to getting back into the match. Marchisio chips the ball into the box and Morata chests the ball down to Tevez. The Argentine then heads the ball back into the path of Morata, who finds himself a yard to fire in a strike, but Roberto is equal to his effort and brilliantly palms the ball clear.
66 minYELLOW CARD! In the midst all of that action, Marchisio ended up picking up a booking for bringing down Kasami.
69 minSUBSTITUTION: Olympiacos make their first change of the match, with Afellay coming on to replace Mitroglou.
72 minCHANCE Morata has had the visitors' best chances of the half and he comes close again when Vidal picks him out with a great cross into the box, but he ends up directing his header over the bar.
74 minSAVE! Juventus are really starting to pile on the pressure now and all the chances are falling Morata's way. The Spaniard is slipped into the box by Tevez and from a tight angle he gets in a low drive, but once again Roberto is equal to his attempt and makes the save.
75 minOFF THE BAR! It's all Juventus at the moment and Pogba almost catches the keeper out with a cross into the box that floats over everyone and comes back off the bar. Moments later Pogba chips another ball into the middle that eventually drops to Tevez, but once again Roberto is there to block the shot.
77 minSUBSTITUTION: Juventus are throwing everything at Olympiacos now and Pereyra is on to replace Ogbonna.
80 minSAVE! This is turning into the Roberto show now, as the Olympiacos goalkeeper makes another outstanding save. Pogba teases another cross into the middle that heads all the way through and the keeper manages to tip the ball wide for a corner.
80 minOFF THE BAR! This is the save of the night from Roberto. Juventus whip a corner into the box and it drops kindly to Marchisio, who then fires in a powerful strike. The ball looks as if it's heading in, but the keeper gets his fingertips to the ball to turn it onto the bar. If Olympiacos do manage to hold on, then they will owe a great deal to the man between the sticks.
83 minOver the past couple of minutes Olympiacos have been able to relieve the pressure and see some of the ball in the Juventus half. There is surely going to be more late pressure from the visitors, but it remains to be seen whether they can beat the outstanding Roberto.
85 minSUBSTITUTION: Olympiacos make their second change, with Fuster coming on for Dominguez.
86 minSAVE! Yet again Roberto comes to the home side's rescue. This time Tevez is the man who is denied, as he cuts inside and fires in a low strike, but Roberto gets down and palms the ball away at full stretch.
87 minSUBSTITUTION: It's the last throw of the dice for Juventus, as Giovinco replaces Pogba.
90 minSUBSTITUTION: Giannoulis is on for Olympiacos, with the goalscorer Kasami heading off.
90 minThere are going to be four minutes of stoppage time.
90+2 minJuventus are piling everyone forward, but they are still unable to find a way through the home defence. Even when they have managed to get in behind this evening, they have been stopped time and time again by the keeper.
90+4 minFULL-TIME: Olympiacos 1-0 Juventus
9.38pmIt's all over in Athens and Olympiacos have pulled off a fantastic result by beating Juventus 1-0. Kasami's goal was all that separated the teams, but the true hero this evening was goalkeeper Roberto, who was simply unbeatable.
9.41pmAllegri will wonder how his side didn't find the net, but there was no answer to the quality of Roberto. In tonight's other Group A match, Atletico Madrid have comfortably beaten Malmo 5-0 in Spain. It means that Olympiacos and Atletico top the group on six points after their first three matches.
9.44pmThat's all we've got time for here. Please stay with us for results and reaction from every match that took place in the Champions League this evening. Until next time, goodbye!