Work will involve revamping the office building at One Puddle Dock, near Blackfriars Station, and was secured with a bid of £20.6m.
The win is the latest in a series of jobs secured by Willmott Dixon as it targets the green office retrofit sector, and was secured against rival bids from Mace, Overbury, ISG and BAM.
The offices were previously part occupied by Balfour Beatty’ Blackfriars Bridge station project team.
Now Willmott Dixon will refurbish the six-storey office block to create a new home for 580 Network Rail staff and new shops on the ground floor.
The job involves a complete strip out of M&E services and replacement of existing glazing to achieve a BREEAM Excellent rating.
Willmott Dixon will also create a new extra plaza area as part of the 11-month overhaul.