The Catchphrase host will front Big Star's Little Star, in which Britain's best-loved stars team up with their own children to win money for charity.
The show also promises to give viewers a peak into each star's home life, possibly revealing "embarrassing secrets" and "cringeworthy crushes".
"Big Star's Little Star is a really lovely new show where kids talk about their famous mums and dads," said Mulhern.
"Everyone's a winner and even the viewers can play along. I can't wait to hear the funny stories and anecdotes about some of our best loved stars from the people who know them best... their kids!"
Elaine Bedell, ITV's Director of Comedy and Entertainment, added: "Stephen is a fantastic talent, and a brilliant host for this show, which is a real family entertainment gem."
Mulhern's recent Catchphrase revival proved a hit for ITV,