The listed company has agreed a deal to move into a new headquarters development close to Regent Street, from its present home in two offices on Berkeley Square.
Jeremy Helsby, chief executive of Savills, said the deal "is a strong expression of confidence in the Savills business going forward and in London as a global financial centre".
He added: "This move will provide Savills with an exciting new London headquarters building for the future benefit of both our staff and our clients."
The pre-let agreement with Great Portland Estates, which is redeveloping the 33 Margaret Street site, is a boost for London because there has been a slowdown in letting deals with businesses reluctant to commit to new office space.
Savills has signed up for 20-year leases on 64,142 sq ft of office space, out of a total of 102,291 sq ft. The company will pay rent of £68.60 per sq ft and also enjoy a 30-month rent-free period
Toby Courtauld, chief executive of GPE, said: "We are delighted to welcome Savills to 33 Margaret Street. As one of the UK's pre-eminent real estate advisory businesses, their move provides a strong endorsement for the quality of the building and we look forward to working with the Savills team to create their new London headquarters."