The Islington seafood bar, which also runs a restaurant in Padstow, has taken on the former LeCoq site near Highbury & Islington tube station.
Prawn on the Lawn was launched in London by former Fishworks manager Rick Toogood and his wife Katie in 2013, and has since been extended to include a 16-cover basement restaurant.
As its current site lacks a proper kitchen Londoners have only enjoyed cold dishes such as scallop ceviche and oysters until now, but the new opening will allow the restaurant to offer a full hot food menu.
Dishes will depend on the catch of the day that comes in from Cornwall, but the menu at Prawn on the Lawn Padstow can include a half lobster with tomato, garlic and tarragon salad; monkfish and chorizo stew with homemade soda bread; and marinated scallops cooked over coals.
The current London site will close on 22 April with the restaurant relaunching at its new location on 27 April.