Six days after going down 4-1 to Arsenal in the final, Leeds slid to a more unexpected defeat as the Bluebirds claimed only their third win of the season.
The visitors were twice pegged back after going in front, however, Jess Clarke equalising Natasha Harding's opener then Steph Houghton cancelling out Carla Parfitt's strike.
But the home side were unable to force a third equaliser after Kelly Isaac hit Cardiff's decisive third goal.