Guinan will play the father of Mike (Billy Gardell) when he appears in the CBS comedy, TV Guide reports.
Guinan's character walked out on his family years ago but returns in the run-up to Mike's wedding to Molly (Melissa McCarthy).
Mike & Molly's executive producer Chuck Lorre added that the return of his father will "weigh heavily on Mike's big day".
Guinan recently starred as Governor McCall Cullen in Boss. He has also had guest roles in shows such as The Chicago Code, ER, Grey's Anatomy and The Practice, while his movie credits include parts in The Last Airbender and Hannibal.
Mike & Molly airs on Mondays at 9.30/8.30c on CBS.
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