Bristol City bounced back from their midweek defeat in the Johnstone's Paint Trophy to cross-city rivals Rovers with a win secured by Kevin Betsy's goal.
Betsy scored his first for the club on 19 minutes when he headed in after Northampton goalkeeper Mark Bunn had parried Steve Brooker's fierce drive.
But Bunn kept Town in an entertaining game with saves from defender Jamie McCombe and top scorer Phil Jevons.
Bradley Johnson, with a free-kick, and Kenny Deuchar had Town's best efforts.
Bristol City: Basso, Keogh, Carey, McCombe, Brian Wilson, Skuse, Noble, Johnson (Fontaine 70), Betsy, Brooker (Andrews 78), Smith (Jevons 64).
Subs Not Used: Thomas, Orr.
Booked: Brian Wilson, Carey.
Goals: Betsy 19.
Northampton: Bunn, Pearce, Hughes, Doig, Crowe, Taylor (Hunt 75), Aiston, Bradley Johnson, Holt, Robertson (Kirk 70), Deuchar.
Subs Not Used: Dunn, Jess, Dyche.
Ref: G Hegley (Hertfordshire).