Cheshire-based contractor Pochin will manage and build the new 35,000 sq ft hospital as the developer’s technical partner.
The developer’s bid to build the hospital in Railway Street saw off rivals Nikal and Vinci Construction.
Citybranch now will work closely with the Trust to develop final plans for the new facilities in Altrincham town centre, with a view to begin work on site next summer.
As part of the deal Citybranch will also be given the empty Victorian Altrincham General Hospital site for redevelopment, preserving its historic facade as part of their scheme.
The decision is a setback for Nikal, which had planned to build the hospital as part of its Altair project in Altrincham town centre.
Vinci proposed to build the new hospital on part of the current Altrincham General site.
Cllr Matt Colledge, Conservative leader of Trafford Council, said: “This new hospital is a much needed facility for Altrincham and securing its future has always been the council’s priority.
“Railway Street is an integral part of Altrincham town centre and our ambitious regeneration plans.
“The council has set up a panel of business leaders from across the North West to oversee the regeneration of Altrincham to enhance the appeal of the town centre as a visitor destination by improving the public realm and developing the business, retail and leisure opportunities available.
“We will now be working with the developers to get this much needed facility built as soon as possible.”