The Magpies are now in the midst of their worst run in 27 years, having lost six consecutive top-flight matches.
Below, Sports Mole analyses whether the result was reflective of the action in London.
On target: 8
On target: 3
Was the result fair?
Arsenal were as comfortable as the scoreline suggests. There only looked like being goals at one end, with Newcastle limited to a couple of tame efforts which did not extensively test Wojciech Szczesny. The Gunners attacked well, and the visitors defended poorly. It really is that simple.
From the early stages it was clear that Arsenal would spend a lot of time in the Newcastle half. Their full-backs were constantly providing them with options out wide and sent in plenty of crosses which were not always defended well. Ozil was as lively as he has been in some time, often popping up on the left flank to allow Lukas Podolski to join Giroud in the box, and that was how the Gunners scored their third goal. Unusually it was a set piece that provided Arsene Wenger's side with their opener, but from then on it was their passing game which undid the visitors, and they were always going to create chances with the volume of the ball that they had. On another day, they could have netted a few more.
Alan Pardew's return to the touchline did them no favours, with their defensive positioning and communication as poor as it has been during his time away from the dugout. The basics, such as marking from set pieces and crosses, were poor as errors contributed to all three Arsenal goals. At the other end, Loic Remy, an apparent Arsenal target in the summer, saw very little of the ball as Newcastle failed regularly to get men up in support of him. Yoan Gouffran did on occasion, but could not make the most of the Magpies' two best chances in a performance that was lacking organisation, fight, and ability.
Sports Mole's man of the match
Aaron Ramsey: Who knows where Arsenal would be had this man not spent three months on the sidelines. His energy and willingness to make a variety of runs gives their midfield a completely different dimension and they cleared missed him during his injury absence. Ozil scored and assisted a goal in an improved display, but Aaron Ramsey was the pick of the Arsenal bunch, charging forward from the centre of the park to start attacks and also giving them the physicality to match Newcastle's midfield three.
Mike Williamson stepping up to play offside against a striker as slow as Giroud was ill-advised, and him giving the Frenchman space to get away from the back four helped the Gunners go two goals clear. Giroud messed the chance up himself, but Ozil was on hand to punish Williamson's poor judgement.
Neil Swarbrick's assistant missed Ozil taking up an offside position for Arsenal's second goal, with the German beyond United keeper Tim Krul with only one defender between him and the goal. The free kick awarded for the Gunners' first was also a little soft, so Newcastle may have a few complaints.
Arsenal: The Gunners could have fourth tied down before they host West Bromwich Albion on Sunday, if Everton lose to Manchester City on Saturday, but a win over the Baggies would secure it nonetheless.
Newcastle: Pardew will be desperate for the season to end, but knows that he needs a win between now and then to ease the pressure on him. Relegation-threatened Cardiff City are next up at St James' Park.