The eatery, which introduced vegan cheese back in 2017, has added the new plant-based dishes to over 400 locations in the UK.
Customers can now opt for a Calzone Verdure - featuring roasted peppers, aubergine, and courgette with spinach, smoky tomato harissa, hot chili, tomato with garlic. As well as a Baked Garlic Mushroom side/starter - featuring a whole Portobello mushroom, garlic, vegan mozzarella, rosemary and smoky tomato harissa with rocket, pine kernels, and balsamic dressing.
In Pizza Express' half-year results for 2019, the chain noted the 'expansion of vegan offerings' as one of its 'highlights'.
Jinlong Wang, Group Chairman and Chief Executive Officer of PizzaExpress, said: "We developed our summer menu with a particular focus on our Leggera offering, which provides choices under 600 calories and now extends across our pizza range to tap into the wider trends of health and well-being.
"Our vegan offering has also grown in popularity as we added additional items to the menu."
Pizza Express' vegan menu also features Marinated Green Olives, Rosemary and Garlic Flatbread with Houmous, Chocolate and Amaretto Parfait, Carrot Cake, Sorbet, and a range of pizza and pasta dishes.