ISG has won a £40m contract to carry out the redevelopment of the old Eurostar terminal at Waterloo station.
London and Continental Railways, which develops sites on behalf of the government, is developing £200m worth of retail, leisure and culture units at the station.
As main contractor, ISG will develop up to 135,000 sq ft of space into retail and leisure outlets at the old terminal, which closed 10 years ago.
Work will begin in April 2019, with completion expected in early 2021.
The development will span three floors and below the current platforms and see 40 new glass-fronted units created.
It forms part of the wider redevelopment of Waterloo station funded by Network Rail that will see five of the old Eurostar platforms used for suburban trains.
Waterloo was the London terminal for the Eurostar service until the international station at St Pancras was completed in 2007.
ISG was the main contractor on the £90m fit-out of St Pancras station.
Earlier this month the firm won the contract to deliver a £26m school for the University of Wolverhampton.
Wates had been the preferred bidder for the scheme until it had to be retendered due to scope changes.