Newark and Sherwood District Council plan to restore Newark's Magnus buildings into a museum about the 17th Century war.
The project will cost £5.4m in total and will open in September 2014.
The centre could attract more than 60,000 visitors each year, according to the authority.
Councillor Roger Jackson, the district council's cabinet member for leisure and culture, said: "The new museum will provide a hub for tourism, directing visitors to attractions across the district and Nottinghamshire."
Newark and Sherwood District Council said it has applied to other grant-funding bodies to make up the rest of the money needed.
The authority has worked with the Heritage Lottery Fund to put together plans to renovate the Magnus buildings, part of which date to 1529.
The Royalists surrendered Newark following a siege in 1646 towards the end of the civil war, which resulted in the defeat of King Charles I by the Parliamentarians.
In addition to Civil War displays, exhibition galleries will focus on the local history of the towns and villages of Nottinghamshire.
The Newark Torc, an Iron Age necklace found using a metal detector near the town, will also be displayed in the centre.
It will be the first time the item will be displayed in the district after being loaned to the British Museum.
Buildings in a Nottinghamshire town are set to become a National Civil War Centre after a £3.5m grant from the Heritage Lottery Fund was secured.