Spears is currently serving as a judge on the reality show, which recently held auditions in San Francisco, California.
Don Phillips, a singer who provided vocals on the duet 'I Will Still Love You' from Spears's debut album Baby One More Time, took to the stage for a shot on the programme.
A source told Perez Hilton that Spears instantly recognised the singer, and adds: "She got this huge smile on her face and her eyes lit up. It was so sweet.
"When he started crying and saying he thought he'd never see her again and that he'd had a lot to deal with, Britney was comforting him to calm him."
Phillips's audition ultimately did not go well, the insider claimed, but he apparently took the opportunity while on stage to come out to Spears as gay.
"You could tell she was emotional and she really felt for him especially when he was crying," the source explains. "But she also stayed calm. She handled it unbelievably well and really stepped up to the situation."
Fox recently announced that The X Factor USA's second season will premiere over two nights on Wednesday, September 12 and Thursday, September 13.