While Roberto Di Matteo's team of millionaires won the FA Cup at Wembley and added the Champions League title by beating Bayern Munich, who they beat on spot-kicks, Matt Beard's side could not manage to add another title to the club's collection.
Instead it was Birmingham lifting their first Women's FA Cup, at Bristol City's Ashton Gate.
Chelsea went ahead through Helen Lander after 68 minutes, and looked certain winners until Rachel Williams hit a stoppage-time leveller.
The London side moved in front again in the 102nd minute when substitute Kate Longhurst struck, but a free-kick from Karen Carney hauled Birmingham back to 2-2 with nine minutes of extra-time remaining.
It came down to spot-kicks and Birmingham were the more assured takers, missing only their first when Williams saw a tame sidefooted shot easily gathered.
Rachel Unitt, Jodie Taylor and Carney stepped up to score for the midlands side, with misses for Chelsea from Drew Spence, Claire Rafferty and finally Gemma Bonner, who fired the ninth kick of the shoot-out over the bar, handing the trophy to Birmingham.