The show is set to return to the small screen early next year (14) after an absence of 15 years, and the musician has been hired to play Garthy, the eldest son of Linda Robson's character, Tracey.
Co-star Pauline Quirke will be joined on screen by her real life son Charlie Quirke, who will play Tracey's younger boy Travis.
Willis previously acted as a teenager with small roles in U.K. dramas including The Bill and Casualty. He returned to medical series Casualty for a guest role in an episode which aired earlier this year (13).
He says of his new job, "I'm so excited to be joining Birds of a Feather playing the role of Garthy! I used to watch the show growing up so this is just a dream job. I can't believe I'll be working with (characters) Sharon, Tracey and Dorien."
The comedy, about two sisters who support each other when their husbands are sent to prison, first aired in 1989 and ran for nine years before coming to an end in 1998. It was previously revived as a U.K. touring stage show earlier this year (13).