Historic Baskerville House in Centenary Square will be the new home of Network Rail after it announced plans to bring three separate Birmingham offices together.
The railway owner has agreed to take 85,000 sq ft over three floors at the building next to the Library of Birmingham in one of the largest office deals in the region so far this year.
It will join other corporate occupiers such as Marketing Birmingham and Kaplan Financial at in the building which dates back to the 1930s and was bought by Hermes in 2013.
Network Rail currently has a large presence in The Mailbox and a date for the move is yet to be confirmed.
The Birmingham office of property consultancy JLL led the search for the new offices for Network Rail.
Director Jonathan Carmalt said: "Increasingly, a more strategic approach is required to address an organisation's property needs, particularly public bodies who are under increasing scrutiny.
"While it's important to look for a more cost effective, productive solution, it's also crucial offices meet a client's long-term needs.
"The timing was right for Network Rail to make the move and reassess its property needs as several leases came to a close.
"This did make for fairly complex negotiations to ensure the smooth exit out of three office buildings."
Joint letting agencies for Baskerville House are Knight Frank and CBRE.