Anorak, part of glue London, previously handled the brand's digital production work.
Work Club has been briefed to develop a website for the brand and to create online communications to promote the appointment of the Michelin-starred chef Theo Randall.
Randall will join the company in October to develop a range of "Michelin-starred" pizzas for the company.
The brand's ad account is handled by Isobel, which won the business in March 2007. Up until then, it had used ad agencies on an ad-hoc basis.
Isobel was briefed to create an above- and below-the line campaign for the brand. It has yet to produce any advertising, although it has created menus and posters to promote its authentic Rome menu.
Work Club's managing partner, Martin Brooks, said: "Pizza Express is a truly iconic brand with wonderful creative potential. We can't wait to get stuck in."