The former couple, who dated on and off from 2011 to 2014, were spotted hanging out at her house in Studio City, California, on Sunday.
In photos obtained by TMZ, Bieber is photographed pulling up to Gomez's house in his white Mercedes G-Wagon, 10 minutes before Gomez, wearing a gray sweatsuit and white sneakers, walked in. According to the outlet, the two, as well as other mutual friends, hung out until at least midnight.
Gomez's boyfriend, The Weeknd, meanwhile, has been on tour.
Sunday's hangout isn't the first time Bieber and Gomez crossed paths this year. In February, the two attended Rihanna's GRAMMY after-party at 1OAK in West Hollywood. An eyewitness told ET at the time that Bieber left shortly after arriving, while Gomez was spotted getting intimate with The Weeknd.
And Bieber isn't the only one Gomez has recently reunited with. See her and Demi Lovato's adorable reunion in the video below.