AFL, the firm of architects which designed the Salford City Stadium and 12 Princes Dock, Liverpool, has merged with rival S&P.
AFLS+P has been created through the merger of AFL Architects and S&P.
The company includes the AFL office in Peter Street, Manchester, which employs around 50 people and worked on the Salford City Stadium and 12 Princes Dock, pictured.
S&P did not previously have a North West office.
The deal creates a company with offices in London, Manchester, Glasgow, Dublin and Doha, Qatar.
A new office will open in Birmingham in May this year.
S&P and AFL Architects, both approximately the same size, combine 37 years of experience in masterplanning, architecture, interior design and project management.
Alongside their specialist sector, their work spans healthcare, education, residential, retail and commercial.
Other recent projects include the London 2012 Aquatics Centre, the Peter Makaba Stadium in South Africa and the Abu Dhabi Sports Village.
Keith Ashton, former director of S&P and now one of the six principals of AFLS+P, said: "S&P is a well-established, 22-year old business with an extensive track record in sports and leisure.
"This merger with AFL Architects adds to our skill base and allows us to offer more services to our existing clients internationally.
"All staff at both practices will remain in their current positions and will have the opportunity to work on new and varied projects.
"We also share the same values, with a strong emphasis on developing creative and innovative design solutions that maximise the commercial value and are fit-for-purpose as well as the future," he added.
John Roberts, of AFL and now a Principal of AFLS+P, said: "We have been working collaboratively on projects with S&P for three years.
"Now, with a highly experienced board, we have become one of the largest architectural practices in our specialist sector, we will embrace new opportunities, seek to drive best practice and innovation in the industry and continue to offer an excellent service to our clients.
"Our staff too will have the opportunity to work on new and exciting projects in the UK, and abroad."
The board of directors of AFLS+P are Keith Ashton and Peter Simpson (S&P), and Martin Morton, Phil Osborne, Garry Rowlands and John Roberts (AFL).