The agency won the account after a pitch process that began in April. AIS will now work on a variety of CRM campaigns for Pizza Express.
The restaurant chain has not previously worked with a retained direct agency, but is now keen to increase its DM activity.
Its creative agency is Work Club, which also handles the brand's digital strategy.
Media buying is handled by Manning Gottlieb OMD, while Goodstuff works on the comms planning business.
Pizza Express has used a number of partnership campaigns to help attract customers to its restaurants.
The brand runs a promotion with Orange to offer two-for-one pizzas on Wednesdays, in conjunction with the mobile network's two-for-one cinema ticket deal. It has also run offers in partnership with The Times and on Jazz FM.