City made a sharp start to the game with Leroy Sane threatening early on as his effort cannoned off Aaron Ramsey and went behind for a corner.
Sergio Aguero was the next to try his luck, with seven minutes on the clock when his strike crashed back off Granit Xhaka.
But Arsenal could have been ahead after eight minutes when Ramsey played Mesut Ozil in down the right and his low cross was intercepted by a combination of Kyle Walker and Claudio Bravo, with Pierre-Emerick Aubameyang unable to steer home the rebound.
At the other end, Aguero fired wide before referee Craig Pawson dismissed half-hearted Arsenal penalty appeals after Nacho Monreal had gone to ground inside the City box.
After 18 minutes City took the lead with a route one goal, Bravo's long kick downfield not dealt with by Shkodran Mustafi -- who appealed in vain for a foul -- allowing Aguero to run on and lob the stranded David Ospina.
Ramsey saw a low free kick saved by Bravo before Hector Bellerin went into the book for a foul on Kevin De Bruyne.
Monreal had to come off with a back problem, Sead Kolasinac replacing him, and Ramsey followed him for a high boot soon afterwards.
With half-time approaching, Vincent Kompany produced a superb moment of defending to snuff out the danger when Aubameyang looked to have found a pocket of space before Fernandinho was booked for a foul on Jack Wilshere.
Aguero almost created a second goal for City as the half entered its final five minutes, his cross not dealt with by Arsenal and De Bruyne thumping the dropping ball into the side netting.
Calum Chambers became the latest name into the book when, two minutes into the second half, he pulled back Aguero, and then Kompany saw a strike from the edge of the box deflect agonisingly wide.
City boss Guardiola was forced into a change when Bernardo Silva was replaced by Fernandinho, who appeared to have suffered a muscle strain.
Bravo almost gifted Arsenal a way back into the game when, after 54 minutes, he missed his kick after a long ball forward from Bellerin but recovered to stave off the threat posed by the lurking Aubameyang.
And within moments, City had strengthened their grip on the final, Kompany touching home Ilkay Gundogan's drive after 58 minutes to leave them with one hand on the trophy.
They had both hands on the trophy soon enough as Arsenal disintegrated, David Silva finding space on the left-hand side of the area and belting an angled finish low past Ospina and into the far corner.
Sane threatened to make it four when his pace took him away from Mustafi but he overran the ball and Ospina claimed, and then Xhaka shot over as Arsenal looked for a consolation goal.
Arsene Wenger replaced Ramsey with Alex Iwobi, having already brought on Danny Welbeck for Chambers, with City introducing Gabriel Jesus for Sane.
And with time ticking away Aguero, the man whose goal opened the floodgates, was replaced by youngster Phil Foden as City eased to the most straightforward of victories