The celebrity news website quoted an unnamed insider as saying the on-off pair are back on and attended a July 4 party together in Hollywood.
"They showed up together and left together," the source said.
"They were holding hands and very affectionate," the insider added. "They stayed for about an hour, then left to go horseback riding."
Bieber sparked speculation of a reunion with Gomez after he posted a photo on Instagram last week showing the two of them cuddling.
The singers have dated off and on since 2010, and were widely believed to have broken up for good late last year, although they are occasionally spotted together.