Its branches in Thayer Street and St Bride Street are delivering using waiters, rather than traditional delivery drivers.
Richard Hodgson, PizzaExpress CEO, said: "We’ve been making the best pizzas for 50 years and have built a hugely popular brand.
"This is an enormous growth opportunity and, by extending what we’re already famous for – delicious pizza, great service and excellent value – we can bring about a step change in delivery.
"The pizza delivery market is dominated by American-style, thick-crust pizzas. Thanks to advances in technology, which mean we don’t have to compromise on the quality of our thinner-crust pizzas when in transit, we can now proudly bring to customers’ homes the pizza they love, and in our own unique style."