Argyll and Bute Council said the contract, known as the Waterfront, will also deliver strengthened flood defences and improved public meeting space for residents and visitors.
Work is expected to start on site within the next few weeks with the new building scheduled to open to the public in August 2022.
Councillor Gary Mulvaney, Policy Lead for Finance & Major Projects, said: “The appointment of Heron Brothers marks one of the most significant milestones of this complex project. The award of this contract is the culmination of years of planning, engagement, consultation and due diligence.
“As we emerge from COVID-19 and its global impact, contracts and projects such as the Waterfront development will play an essential part in helping our regional and national economies to recover. As work starts in August, our local economy will benefit from employment and service opportunities.
“It’s a really exciting time for Helensburgh that will not only provide residents with a fantastic facility but also provide a positive draw for visitors and people thinking about moving to the area.”