The office at Oldham Broadway Business Park will be run by Operations Manager Peter Mattimore and Business Development Manager Chris Snow.
Mattimore and Snow worked together for several years at Gleeson Homes in Manchester.
Snow said: “A variety of projects are targeted and early signs are very encouraging with enquiries already in the car retail sector, a major public art gallery extension, primary care facilities, schools extension work and energy services sector.
“We have secured two projects in Cumbria, a Community Hospital at Cockermouth with a construction value of £9.4m and a Health Centre at Cleator Moor, circa £4.2m.
“Robertson has an excellent track record in health care construction and this area will be particularly targeted and we will also be looking for contracts in the commercial and industrial sectors.
“Developing existing Robertson relationships with clients and consultants who have operations in the north west of England will also be important in growing the business.”
Andrew Cowan, CEO of Robertson Group said: “The opening of the Manchester office forms part of our business strategy to create regional operational centres.
“This new office demonstrates our commitment to the area and our clients and our determination to continue growth locally.”