Rufus Leonard will handle all digital creative and strategic projects for Pizza Express, as well as putting together a new website. The incumbent on the account is Maynard Malone.
The move is part of a broader review in-house by the restaurant chain, which was sold to Hony Capital, a Chinese private equity firm, in July.
Neil Svensen, the chief executive, co-founder and chief creative officer at Rufus Leonard, said: "Pizza Express is one of the nation's most loved brands.
"They have a brilliant product and some serious ambitions to take this and deliver the best digital restaurant experience possible.
"We're really excited about the work we've got coming up. There's also the massive positive for everybody at Rufus of Sloppy Giuseppe becoming the late night food of choice."
The7Stars, the media agency for Pizza Express will not be affected by the changes.