The "Blank Space" singer, 25, wore brown shorts and a loose printed top with her hair down and her make-up minimal. Clutching a Diet Coke in her hand and passionately singing along with close friend Alana Haim, Swift seemed to be having a ball at her show, reported Us magazine.
Swift, 25, recently kicked off her 1989 World Tour in Tokyo, with her next show on May 15 in Las Vegas.
The singer and Harris have been spotted out together several times since their dating reports emerged in April.