The job was procured under the P23 framework, and Willmott Dixon is working with Ryder Architecture, Edmond Shipway & Partners and Hydrock Consultants as part of its wider team.
The new Bristol unit will be run by Avon and Wiltshire Mental Health Partnership NHS Trust and complements another similar facility currently under construction in Devon.
It will be able to support up to 10 patients at any time, with the building specifically intended for those whose needs cannot be met by existing hospital or community-based services.