Pierre-Emerick Aubameyang, Nicolas Pepe, Mesut Ozil and Alexandre Lacazette were all on target after the break as the hosts secured what was ultimately a convincing win in North London to end a run of four successive draws in the Premier League.
The Magpies had the best chance in what was a fairly tame first half as Joelinton fired wide when well placed after quarter-of-an-hour, while Shkodran Mustafi came close from a corner as the interval approached.
Arsenal started the second half with more purpose and Newcastle were handed an early warning when Eddie Nketiah clipped the crossbar.
Aubameyang then headed home the opener nine minutes after the restart after Pepe picked him out with a delicious in-swinging cross from the right flank.
Pepe doubled their advantage three minutes later as he slotted home from close range following some trickery from Bukayo Saka.
The 18-year-old bamboozled Newcastle defender Valentino Lazaro, slotting the ball through the legs of the man on-loan from Inter Milan before racing into space and picking out Pepe.
The visitors tried to respond and came close to reducing the deficit with 15 minutes of normal time remaining but Allan Saint-Maximin was denied by the woodwork.
Ozil poked in a third late on to end any hope of a comeback from Newcastle after good work from substitute Lacazette.
There was still time for the Frenchman to get on the score sheet himself as Joe Willock and Pepe combined to set up Lacazette, who rather fortuitously miscued a first-time right-footed effort of his left foot then into the top corner with virtually the last kick of the game