Left back David Murphy gave Blues a 1-0 lead just past the half hour mark at Pride Park when he headed home from a Larsson corner.
Larsson himself doubled Blues' advantage just a minute into the second half when Rams' goalkeeper Stephen Bywater's attempted clearance from inside his box bounced off the Blues winger and found the empty net.
The home side reduced the deficit on 57 minutes when left-back Gareth Roberts beat Ben Foster in the Blues goal with a superb shot from just outside the penalty box.
Blues had a great chance to make the scoreline 3-1 in the dying seconds but second half substitute Kevin Phillips failed to find the net with a header from close range following good work on the right wing from Cameron Jerome.
Derby: Bywater, Brayford, Roberts (Moxey 60), Green (Doyle 83), Leacock, Anderson, Cywka (Pringle 70), Savage, Porter (Hulse 64), Commons, Bailey. Subs not used: Deeney, Martin, Buxton, Varney.
Blues: Foster; Parnaby, Murphy, Johnson, Dann; Larsson (McFadden, 66), Gardner, Ferguson, Fahey; O'Connor (Phillips 74), Nikola Zigic (Jerome 66). Subs not used: Taylor, Carr, Bowyer, Ridgewell, Kerr, Michel, Valles, Mutch.
Referee: Mark Halsey