The "Shake It Off" singer was at the star-studded event in Los Angeles on Thursday night (November 15), and was with her beau of around two years at the after-party all night, according to reporters at People.com.
Emma Stone, who stars alongside Joe in the movie, was also spotted talking to Taylor at the bash.
The 28-year-old singer was previously seen by the side of Joe, 27, back in September at the New York Film Festival premiere of the Yorgos Lanthimos-directed film, which also stars Rachel Weisz and Olivia Colman.
Emma and Rachel play rivals in period drama "The Favourite", which follows Queen Anne, played by Olivia, as she prepares for war with France.
Both Taylor and Joe have been supportive of one another's careers, with the British actor being seen in the audience at several of the singer's "Reputation" tour stops across the United States.
While the couple is notoriously private about their romance, Joe briefly opened up about his girlfriend's political stance on the U.S. midterm elections.
"I think it's great, I think it's important," he told a reporter in October when asked about Taylor's encouragement for early voting and her endorsement of two Democratic candidates in her adopted Tennessee.