The episode will air on Sept. 23, Jackson told syndicated entertainment TV show "Access Hollywood" in an interview that aired Monday.
Her last prime-time role was as Cleo Hewitt on NBC's "Fame" (1984-85). She also appeared in the TV shows "Diff'rent Strokes" (search) and "Good Times."
When asked about the upcoming "Will & Grace" episode, Jackson said it involves Sean Hayes' character, Jack McFarland, "trying out as a dancer."
"There's a little bit of a routine and they go on to do their thing from there," she said in excerpts of the interview posted on the "Access Hollywood" Web site. "It's so funny. I have to catch myself because I'm cracking up in rehearsals. It's just funny to watch them. It's hilarious."
Jackson's breast-baring performance during the halftime show at this year's Super Bowl, seen by millions of TV viewers, created an uproar.
Her new album, "Damita Jo," (search) was released in March.