Ryan Fredericks was sent off as Birmingham secured their first win under Gianfranco Zola.
Fredericks was red-carded on 68 minutes for a reckless challenge on Craig Gardner.
Lukas Jutkiewicz scored eight minutes later after being set up by Cheick Keita’s cross.
The Blues had not won in 10 matches since Zola was appointed following the sacking of Gary Rowett.
And their wait might have continued had Floyd Ayite not missed a great chance to equalise in injury time.
Ayite fired wide of the target after Chris Martin and Lucas Piazon had gone close for the visitors with second-half headers.
Earlier, Jutkiewicz headed against the bar from close range.
The defeat means Fulham drop to 10th in the Championship table – six points adrift of the play-off places.
This post was last modified on 04/02/2017