CheethambellJWT, the incumbent on the account for 13 years, was not invited to repitch.
TBWA will be working on briefs for the theme parks Alton Towers, Thorpe Park and Chessington World of Adventures, as well as Warwick Castle.
Next year, advertising will cover the whole range of attractions, with a particular focus on new rides that are being introduced at Alton Towers and Thorpe Park.
Other Tussaud's attractions, including Madame Tussaud's and the London Eye, were not included in the review and Heresy will continue to create work to promote them.
Andy Edge, the sales and marketing director at The Tussaud's Group and TBWA's former Holsten client, said: "As Europe's largest visitor attraction group, we are committed to substantially growing our attractions through a combination of innovative product development and groundbreaking marketing initiatives."
He added: "We are looking forward to working with TBWA on the next stage of our attractions' exciting growth agenda."
Andrew McGuinness, the chief executive of TBWA\London, said: "It's been a hard-fought pitch against some great agencies.
"We're delighted to have won the business - it's a great opportunity and promises to be great fun."
In the UK, The Tussaud's Group attracts around 15 million customers a year.
It is also working on the roll-out of the brand in Europe, Asia and the US, where it has already launched a number of visitor attractions.