Swift made the endorsement in a post on Instagram and said she will vote for the U.S. vice president in the Nov. 5 U.S. elections which polls show to be very tight.
Swift's post included an image of the singer with a cat and her statement was signed off as "childless cat lady" in an apparent dig at remarks previously made by Trump's running mate JD Vance.
Harris' running mate Tim Walz was on air on MSNBC when the endorsement was announced and he was asked about it.
"Get things going," Walz said in an appeal to "Swifties" on MSNBC when asked about her endorsement. "I am incredibly grateful," Walz said.
