"Half my friends don't even know this," People magazine quoted Spelling as saying on Saturday's edition of Tori Spelling: Celebrity Lie Detector.
"It was a summer fling. It was off set. It was our version of, like, a summer romance, the 90210 version and that was it," she said. "You know, we stayed great friends for the rest of the run, and beyond that, but, yeah, we had that one summer fling."
Spelling's and Priestley's characters Donna and Brandon never dated on the show.
During her weekend confession, Spelling -- now a 42-year-old, married mother of four children -- also confirmed she and Brian Austin Green, who played Donna's longtime beau David on the series, had at one time been a real-life couple.
The series ran 1990-2000, and was revived with a new cast 2008-13.