The London-based law firm has taken a 5,300 sq ft office in Central Park Business Centre in East Manchester on a 10-year lease.
The legal practice specialises in personal injury, employment and human rights. Leigh Day first took temporary space in Central Park in April, and has now expanded into a larger office.
Fujitsu is the landlord, and was advised by Colliers International. Leigh Day was represented by AKM Property Consultants.
Quoting rent in the building is £16.50/sq ft.
Rupert Barron, director and head of the tenant advisory team at the Manchester office of Colliers, said: "Leigh Day Solicitors is a successful law firm that planned to take a smaller amount of space at Unit C to accommodate its growth plans thanks to a burgeoning case load but found itself expanding ahead of expectations and in need of larger office facilities.
"The firm's growth and the planned opening of an office in Manchester by international law firm Nabarro helps to cement the city's status as the centre of legal excellence outside of London with a dynamic legal sector."