The 'Star Wars' icon told ET that he was "blissfully unaware" of the fling, and he's happy about that.
Carrie Fisher recently revealed that she and Harrison Ford carried on a wild affair on the set of the original Star Wars back in the 1970s, but the whole thing apparently flew under Mark Hamill's radar.
The iconic star spoke with ET's Ashley Crossan at the premiere event for launch of the Comic Con HQ network at the Paley Center in Los Angeles on Tuesday where he said he "was blissfully unaware" that his co-stars were having a fling.
"I was so self-involved at that point, they could've been doing it in front of me and I wouldn't have noticed," Hamill, 65, joked. "I was single and had my own agenda."
WATCH: Mark Hamill Tells New Stories from 'Star Wars'
While he says that on-set romances are "commonplace," Hamill explained how "tricky" they can end up being for everyone involved.
"If the relationship doesn't last and you're on a TV series and you got four more seasons to go, it can be really awkward," Hamill shared, from personal experience.
"It happened to me. I was with a girl who was playing my sister on a soap opera, General Hospital," he recalled, referring to his short-lived romance with co-star Anne Wyndham in the early 1970s. The actor married wife Marilou, a dental hygienist, in 1978.
Ultimately, Hamill said he's glad he didn't know about Fisher and Ford's relationship at the time, as it would have only gotten in the way of production.
"I think it might have been a distraction if I'd known what was going on," Hamill admitted.
WATCH: Carrie Fisher Reveals How She Kept Harrison Ford Affair a Secret for 40 Years
Fisher detailed her affair with the then-married Ford in her recently released memoir, The Princess Diarist. Check out the video below to hear more about how they struck up their on-set relationship.
While Hamill is set to star in the upcoming Star Wars: Episode 8, the sci-fi icon is currently hosting an online series, Mark Hamill's Pop Culture Quest. In the show, Hamill travels the country to meet other pop culture enthusiasts and collectors who dedicate their lives to celebrating their passion and fascinations.
"There's a certain shared passion that we have," Hamill said of getting to meet so many different collectors and hobbyists. "It's universal. It doesn't matter if I don't collect a specific item that you collect. We have the same motivation in terms of collecting."
Mark Hamill's Pop Culture Quest is now streaming on Comic Con HQ.