Work is starting on the £50m Building A, the first of three potential buildings across the waterside development, which will consist of 200,000 sqft of office and retail space.
The site overlooks the Avon, adjacent to Temple Way near the city centre.
The building includes range of flexible office spaces designed for both local and global businesses in the services, creative, consultancy, financial, media and technology sectors.
Building A will be completed at the same time as a major new waterfront public space, which will be home to a rolling programme of events, public art and outdoor green places and connections by waterfront walkway to the rest of the city.
Galliford Try previously worked with Bell Hammer at the award-winning Forbury Place development in Reading.
Simon Burton, managing director of Building West Midlands and South West, said: “The Assembly Bristol development is one of the most prestigious projects in the city centre and the wider region.”