The match was disrupted by rain, but the world number two kept his cool to beat the world number 44 in straight sets.
Djokovic, who has never won the title at Roland Garros, will face France's Jeremy Chardy in the next round.
Read how all the action unfolded below:
12.35pmGood afternoon. World number two Novak Djokovic should be making his way onto Philippe Chatrier court at Roland Garros in the next few minutes to get his French Open campaign underway against Portugal's Joao Sousa.
12.37pmThere has been some rain around Paris this morning, with the start of today's schedule having been delayed by an hour. The sky is getting a bit dark again so there's a chance that this match could be interrupted should the showers return. There are a few drops falling at the moment, but play is continuing on the other courts.
12.40pmDjokovic has performed well at the French Open in recent years, but is yet to win the title. He made the final in 2012, and had four other semi-final appearances, including last year when he lost on epic last-four match against eventual champion Rafael Nadal. Djokovic beat Nadal on clay earlier this month, so will be hoping that this is his year to complete the career Grand Slam.
12.43pmSousa has faced Djokovic just once before, at last year's US Open. The Serb won that match in straight sets, allowing Sousa to claim just four games. With the weather forecast for today, Djokovic will be hoping for a similarly swift match against the world number 44 today.
12.46pmIt's looking like there might be a bit of a delay to this match. The rain has started to fall a little heavier and the players are yet to make their way out. There's been no announcement from the tournament officials, so hopefully this is just a short delay while the shower passes over.
12.49pmThere's already been one match completed on Chatrier this morning, with former champion Maria Sharapova cruising past Ksenia Pervak in straight sets. You can catch up with all of our French Open coverage here while we're waiting to see if this match is going to get started.
12.53pmWhile Sousa has not been a regular competitor at Masters events in the last couple of years, he has had quite a bit of success on the challengers circuit. His game suits the clay, helping him to eight tournament wins on the surface.
12.56pmDjokovic and his coach Boris Becker have both been waiting in the corridor leading up to the court while this delay continues, they're clearly both keen to get the match underway. Play has continued on every other court and the covers haven't been brought out on Chatrier.
12.58pmGood news! The rain has passed and Djokovic is finally getting ready to make his way out, along with Sousa.
1pmThe players are now on court so the match will be getting underway shortly. As they didn't have the chance to practice on one of the outside courts due to the weather conditions earlier, the duo will be given 10 minutes to get used to the conditions before the first game begins.
1.03pmSousa has played in the recent Masters events on clay in preparation for this match. However, he lost in the first round at Rome, Madrid and Barcelona, so he hasn't had much time to tune his game to this surface.
1.05pmDjokovic's preparations for this event have been much more fruitful. He won the Rome Masters, but struggled with a wrist injury in the semi-final of the Monte Carlo event, which prevented him from playing in Madrid.
1.05pmRight then, they're finally ready to get the match underway, with the second seed to serve first.
Sousa *0-1 DjokovicDjokovic is immediately under pressure as he makes two mistakes with drop shots to give Sousa a 30-0 lead. He responds swiftly with an ace before a poor backhand from Sousa levels the scores. The Portuguese struggles with his backhand again, firing his next two into the net to give Djokovic the hold. It's a shaky start for the Serb but he's off the mark.
Sousa 0-2* DjokovicBREAK! Djokovic claims the opening couple of points before Sousa fights back, but another backhand mistake gives the world number two a chance to break. Sousa forces a poor return from Djokovic to save the point, but he eventually concedes when Djokovic forces a long forehand from the world number 44, giving the Serb a break following an epic nine-minute game.
Sousa *0-3 DjokovicTwo aces and a poor Sousa backhand quickly give Djokovic a 40-0 lead, and he quickly wraps it up when Sousa slices his backhand wide. The Portuguese seems keen to use the shot, but it really hasn't done him any favours so far.
Sousa 0-4* DjokovicBREAK! Djokovic is on the attack again as he takes a 40-30 lead to give himself a chance for a double break. Sousa's sloppy backhand lets him down again as he tries to force the game to deuce, gifting Djokovic the game. So far this has been pretty comfortable stuff for the second seed.
Sousa *1-4 DjokovicBREAK! Djokovic is starting to try some more ambitious shots as he seeks to wrap this set up as quickly as possible, but a couple of loose forehands give Sousa a chance to get a break back. Djokovic fires an ace past his opponent to save the first, but his backhand drifts just wide while looking to save the second, giving Sousa his first game of the match.
1.31pmPLAY SUSPENDED! The players are heading off court because the rain has returned. It looks like it's quite a heavy shower, and the ground staff appear to be getting ready to cover the court. This could be a lengthy break.
1.33pmActually, the rain has already started to get lighter, and the court is being swept rather than covered at the moment, so hopefully this will be a short break.
1.37pmWhile we're waiting to see if play if going to restart, let's take a look at some of the stats from the first five games. Djokovic has made four aces so far, while Sousa is yet to make any. 60% of the Serb's first serves have been in, which is the same percentage as his opponent.
1.40pmThe second seed has made six winners and seven unforced errors, while Sousa has just two winners and 11 unforced errors, most of which have come from his backhand, which really hasn't been up to scratch so far.
1.44pmSousa looks like he is in danger of suffering another heavy defeat at the hands of Djokovic, following his 6-0 6-2 6-2 loss to the world number to in last year's US Open. The break back that he secured just before the break will give him some hope though, but he'll need to figure out what's going wrong with his backhand while he's off the court.
1.49pmWhen this match is eventually completed, the winner will be facing Jeremy Chardy in the next round. The Frenchman, who should have the support of the home crowd, eased past Spain's Daniel Gimeno-Traver in straight sets yesterday.
1.53pmWell it looks like this delay is going to be a bit longer than we'd hoped so we're going to pause our live coverage of this match until there's some more action to bring you. Join us again later when the sun is back out, until then, goodbye.
2.40pmGood news! The covers are off, the rain has eased off and the players are back on court! They'll need a couple of minutes to warm up, having been off court for about an hour now, but we should be back underway shortly.
2.42pmIt's looking a lot brighter around Paris now than it was when this match got underway. Even during Sharapova's match earlier it looked like rain was always imminent, but there's a hint of blue sky now, so hopefully the weather will let this match reach it's conclusion this afternoon.
2.43pmRight, the players are ready to begin, with Sousa serving in the sixth game of the first set.
Sousa 1-5* DjokovicBREAK! Djokovic makes a lively start, showing great movement as he rushes into the net to slice a backhand volley past his opponent. A wide forehand from Sousa gives Djokovic an immediate chance to restore his double break, and he does when Sousa wildly blasts his backhand long.
2.50pmDjokovic makes a string of mistakes as he tries to serve out the set, giving Sousa three break points. However, he reacts quickly, getting the better of the Portuguese with a fantastic cross-court forehand before firing an ace down the centre. Having pulled it back to deuce, Sousa's backhand troubles continue, giving the second seed a set point, which he takes when Sousa smashes he return wide. It feels longer with the rain break, but that took Djokovic just over half an hour.
Sousa 1-6 1-0* DjokovicSousa makes a solid start to the second set, comfortably holding serve for the first time in this match. A couple of errors from Djokovic help him out, but a well-timed forehand and a rare backhand winner ensure that he seals the game.
Sousa 1-6 *1-1 DjokovicDjokovic also makes a strong start to the set on serve, claiming the opening point with a solid forehand before forcing a couple of poor returns from Sousa and wrapping it up with a stunning smash at the net.
Sousa 1-6 2-1* DjokovicDjokovic takes a lucky 30-0 lead as he mis-hits a cross-court volley, but Sousa isn't quite fast enough as he makes the return. The Serb is let down by a couple of errors at the net, hitting back-to-back backhands into the net to allow Sousa to level the scores. The Portuguese finally seems to be finding some rhythm as he comes into the net to smash his forehand past Djokovic before a mistake from the world number two gives Sousa the hold. Djokovic looks a little sloppy during that game, which may have given his opponent hope of staying with him in the second set.
Sousa 1-6 *2-2 DjokovicOnce again it's a hold for Djokovic, but it's not as comfortable as his previous game, with Sousa looking ever more confident. However, at 30-30, the Serb takes the lead with an ace, before sealing the game with a powerful forehand winner.
Sousa 1-6 2-3* DjokovicBREAK! Sousa will be disappointed to have given away the break, having looked much more comfortable at the start of this second set. The Portuguese started the game well, but a double fault at 30-0 let Djokovic back into the game. A couple of errors from Sousa gave Djokovic break point, and he gave the game away with another double fault while trying to force deuce.
Sousa 1-6 *2-4 DjokovicThe errors are starting to creep back in for Sousa now. He struggled with his backhand before the rain delay and it's really costing him again now. Djokovic finds a superb forehand winner to help him to a 40-0 lead before Sousa slices his backhand into the net.
Sousa 1-6 2-5* DjokovicBREAK! Sousa starts the game well with a solid forehand winner, but Djokovic soon responds. The pair both make forehand errors as the game heads to deuce, with Djokovic's costing him a break point. After a couple of advantages for Sousa, Djokovic get another chance to break, and he takes it by coming into the net to smash the ball past his opponent. The second seed will serve for a two-set lead next.
3.18pmA couple of umbrellas have started to go up in the crowd as the rain returns around Roland Garros. It's only light at the moment, but the umpire has decided to hold the players to see if it passes. This must be so frustrating for the players.
3.20pmIt's falling quite steadily now, but the umpire is keeping the players in the seats on court. Djokovic looks pretty relaxed as he puts his rain coat on and jokes around with one of the ball boys.
3.22pmDjokovic is really enjoying himself while they wait for the rain to pass. He invites the ball boy to sit next to him and hands him a racquet. The pair chat for a couple of miuntes before the Serb hands the lad a bottle of water, much to the amusement of the crowd. Sousa seems a little more serious as he sits with a focused expression under an umbrella.
3.23pmThe umbrellas are back down and play is about to continue with Djokovic serving for the second set.
3.29pmDjokovic's relaxed approach to the shower seems to have cost him as he makes a string of backhand errors, giving Sousa two break points. However, the Portuguese has a similar issue, firing his backhand wide to save the first before the world number two finds the sideline to bring up deuce. Djokovic finds his focus to give himself a set point with a forehand winner to the back of the court, before sealing the set with an ace.
3.30pmDjokovic has one foot in the second round now, Sousa has only been involved in two five-set matches during his career, and has never come from two sets down to win.
Sousa 1-6 2-6 1-0* DjokovicDjokovic pushes hard for an early break in what could be the final set, as the Serb makes a sliced backhand and forehand smash to take the game to deuce, but and error gives Sousa advantage, and he holds the game when Djokovic returns his serve to the net.
3.36pmHere's a shot of Djokovic sharing his seat, umbrella and water with a ball ball during the brief rain dleay during the second set.
Sousa 1-6 2-6 *1-1 DjokovicDjokovic still doesn't look completely settled, as he follows up an ace in the opening point of the game with a double fault. However, his remaining serves are all well-placed, forcing a string of poor returns from Sousa to give Djokovic the game.
Sousa 1-6 2-6 1-2* DjokovicBREAK! Djokovic makes some superb returns as he quickly claims a 40-15 lead to leave his opponent facing two break points. The Portuguese shows fantastic determination as he forces a backhand winner to save the first, but a careless forehand into the net gives the second seed the break.
Sousa 1-6 2-6 *1-3 DjokovicThe world number two easily consolidates his break of serve as he pushes for a straight sets win. Sousa is starting to struggle now and gives away the game, failing to get a single return in.
Sousa 1-6 2-6 1-4* DjokovicBREAK! Djokovic has found another level in the last couple of days and is now absolutely cruising. He moves inside the baseline to send a backhand past his opponent before smashing a forehand from the net. Facing another three break points, Sousa tries to keep himself in the set by forcing a couple of errors from his opponent, but Djokovic is too good as he wraps the game up with a forehand down the line. It's difficult to see any way back into this for the Portuguese now.
Sousa 1-6 2-6 *2-4 DjokovicBREAK! Sousa is given some hope when Djokovic makes his second double fault of the match before he catches the Serb out with a trick volley to bring up deuce. The second seed has to face his first break point of the third set when the world number 44 hits a superb forehand, but he saves it with some smart play at the net. However, Sousa isn't going down without fight, and he makes a pair of fantastic forehands to get a game back.
Sousa 1-6 2-6 2-5* DjokovicBREAK! Djokovic is straight back to his double break lead after a blip in the previous game, using a range of shots, including a backhand volley at the net to leave himself just one game from a place in the second round.
Sousa 1-6 2-6 *3-5 DjokovicBREAK! Djokovic is showing some inconsistencies as he tries to see this match out. He takes a 30-0 lead as he serves for the match, but Sousa starts to attack, forcing more errors from the second seed to give the Portuguese the game. Djokovic will certainly need to improve is he's to go on to be a contender at these championships.
Sousa 1-6 2-6 4-5* DjokovicSousa holds serve comfortably as Djokovic fails to pick up a single point, but he'll have the chance to close the match out on his own serve next.
4.08pmA forehand winner give Djokovic two match points. Sousa fights to save the first, but he can't stop Djokovic's serve on the next point as the Serb wraps it up with an ace. It wasn't the best match the world number two has ever played, particularly in the final set, but he'll be relieved to be through in straight sets given the weather conditions.
4.10pmNext up for Djokovic is Jeremy Chardy. The Frenchman could be a tricky opponent on the clay, so the Serbian will need to cut down the errors next time out if he's to progress smoothly again.
4.12pmWell that's all from this match, but stick around for coverage of defending champion Rafael Nadal's first-round match which should be getting underway in the next few minutes. Thanks for joining me this afternoon, goodbye