Iris will continue to handle the pizza brand’s social, digital and retail activity.
The agency has worked with Domino’s since 2012, when it was appointed to the digital and direct marketing account. Iris expanded its remit to TV in 2013.
In 2015, Iris created the "Pizza legends" platform, which enabled customers to create their own pizzas. The campaign was credited with generating £3.6m in additional revenue and 38% higher average spend per order for Domino’s.
The review follows the appointment last year of Tony Holdway as sales and marketing director.
Adam Wright, managing partner at Iris, said: "There is no doubt that Iris has had a transformative effect on the business."
Holdway said: "Domino’s is in the final stage of pitching for a new ATL agency."