The builder will improve and expand the town hall complex, originally built at the start of the 20th century to serve Acton’s growing population.
The project includes demolition of Acton’s former baths building, which will be replaced by a new three-storey building housing a 25m swimming pool and a larger gym.
The remaining part of the building will be refurbished to create a new library and council offices.
Chris Tredget, managing director for Willmott Dixon in North London said: “We are delighted to be working with Ealing Council to regenerate another part of Acton by redeveloping the Town Hall.
“We have a long track record in Ealing and are looking forward to adding to that with the improved Acton Town Hall that will be a new focal point on main high street.”