Bristol City eased into the Southern Area final of the Johnstone's Paint Trophy thanks to a goal in each half from Enoch Showunmi and Wayne Andrews.
Showunmi volleyed City into the lead when Brighton let Jamie McAllister's free-kick reach him at the far post.
Andrews made it 2-0 when he converted Jennison Myrie-Williams' cross.
Brighton offered little apart from an early shot from Dean Cox and their goalkeeper Michel Kuipers also made three fine saves to deny Scott Murray.
Bristol City: Basso, Orr, Carey (Keogh 71), McCombe, McAllister, Murray, Skuse, Johnson (Russell 79), Myrie-Williams, Andrews, Showunmi (Fontaine 67).
Subs Not Used: Weale, Noble.
Goals: Showunmi 41, Andrews 68.
Brighton: Kuipers, Hart (O'Cearuill 60), Lynch, Butters (Frutos 79), Rents, Fraser (Chamberlain 72), El-Abd, Hammond, Cox, Robinson, Gatting.
Subs Not Used: Henderson, Elder.
Booked: El-Abd, Hart.
Ref: T Bates (Staffordshire).