The Carlyle Group and joint venture partners Nikal and Abstract Securities have let the 20,000 sq ft first phase of their office development in Salford.
Carlyle said it was the biggest letting in Salford Quays since 2010.
VSG will take all five floors of the Boilerhouse, becoming the first occupier at the development.
The Boilerhouse, completed earlier this year, forms the first phase of the 400,000 sq ft redevelopment of the former Colgate-Palmolive factory.
VSG will not be moving from their current office at The Mill, South Hall Street, but will expand the business over two Manchester offices.
Fit-out will start immediately, with the first staff moving in before the end of the year.
Ben Du Boulay, director of the Carlyle Group, said: "This letting is a significant step forwards for the Soapworks regeneration project, and reflects the quality of the space that we have created in this property.
"Having completed and let the Boilerhouse, I am excited about moving onto the next phase of this major regeneration project and creating a new community in Salford Quays."
John Smith, chief executive of VSG, said: "The Boilerhouse met our desires as a business to stay committed to the Salford Quays area as the building is well-located for our staff."
Jones Lang LaSalle and Canning O'Neill are joint agents on the Soapworks scheme.
Nigel Hunter, director of Edwards & Co, advised Vital Services Group.
The Boilerhouse was designed by architects Shed KM.