UPDATE: More details about Taylor Swift and Calvin Harris' backstage behavior have been revealed.
Taylor Swift was again the ultimate fan and cheerleader, this time at 102.7 KIIS-FM's Wango Tango 2015 concert, where she cheered on Calvin Harris as he took the stage.
The 25-year-old "Black Space" pop star and 31-year-old Scottish singer and DJ were later spotted sharing a kiss and holding hands backstage after he finished his set, a source told E! News, adding that the pair left the StubHub Center in Los Angeles together.
"They are cute together. They seem happy," the source said. "They definitely look like they are dating."
The two have sparked romance rumors for months and have been photographed together occasionally, also holding hands, but have never confirmed a relationship.
At Saturday's star-studded concert in Los Angeles, standing backstage, Swift cheered on Harris along with one of her besties, Alana Haim, 23, from the band Haim. Swift and Harris had attended one of the group's concerts in the city in April together and looked rather cozy together.
Ellen K, who is a side host on Ryan Seacrest's KIIS-FM radio show On Air With Ryan Seacrest, said in an Instagram video posted on the program's page that Swift and Harris were spotted holding hands while walking down the hallway at the concert venue.
"They were really happy," she said.
Harris was also joined on stage by Big Sean.
Other performers include Justin Bieber, Kanye West, Fifth Harmony, Meghan Trainor, Jason Derulo, Ne-Yo, Sia, David Guetta and Nick Jonas.