Strikes from Julian Alvarez and Erling Haaland inside the opening 19 minutes left the reigning champions two goals ahead against an under-par Brighton.
On-loan Barcelona attacker Ansu Fati came off the bench to register for the Seagulls in the 73rd minute, but the visitors could not find a second despite finishing with a man advantage due to a late red card for Manuel Akanji.
Jeremy Doku had the game's first half-chance in the sixth minute after smart work from Phil Foden, but the attacker was unable to get his strike on target.
The Citizens were able to make the breakthrough less than one minute later, though, with Doku driving down the left before picking out Alvarez, who found the back of the net from inside the box.
Josko Gvardiol brought a smart save from Brighton goalkeeper Jason Steele in the period that followed before Kaoru Mitoma saw an effort kept out by Stefan Ortega down the other end.
Man City doubled their advantage in the 19th minute of the contest, with Haaland picking up the ball just outside the penalty box before firing a powerful effort into the bottom corner past Steele.
Doku continued to cause Brighton problems and again broke into a dangerous position in the 41st minute, but his cross was excellently defended by Lewis Dunk in the middle of the defence.
Brighton were unable to make their mark in the opening half of action, having just one attempt, with the likes of Mitoma, Evan Ferguson and Joao Pedro largely struggling to get into the game.
The away side's first serious chance of the match came in the 52nd minute when Pascal Gross was released by Simon Adingra inside the Man City box, but the midfielder fired his effort wide of the post.
Haaland came close to his second of the match in the 68th minute, bending one towards the far corner after smart work from Foden, but Steele was on hand to make a brilliant save.
Brighton then halved the deficit in the 73rd minute, with Fati turning the ball into the back of the net from close range after a cross from Mitoma was cleared into his path.
Akanji was sent off late on after picking up a second yellow for a foul on Fati, but the visitors were unable to find a leveller, with Pep Guardiola's side returning to the top of the table courtesy of a narrow win.
Man City will now switch their attention to the Champions League, preparing to travel to Young Boys on Wednesday, while Brighton face Ajax in the Europa League on Thursday.