Seau was accepting the Dolphins' leadership award at the team's annual banquet Wednesday night when he made the remark.
"A joke that came out last night, due to my stupidity, is something we have to deal with today," Seau said Thursday at the team's practice facility. "With that, I am very sad and I apologize."
During his speech at the banquet, Seau said: "We are a unit that cares. ... I would say love and everybody would say, 'You're a faggot,' but I'm not."
It's the second time since joining the Dolphins that Seau's choice of words has sparked controversy.
Last October, Seau -- who is of Samoan descent -- apologized for suggesting the way to stop former teammate LaDainian Tomlinson is to feed him fried chicken and watermelon. Seau said he meant no harm, and Tomlinson, who is black, laughed it off.