An Post has signed a lease that will see it take five floors of The EXO building in Dublin's north docklands.
The building, which is due to be completed at the end of this month, is to become the new headquarters for the state company, once it moves out of the General Post Office (GPO).
An Post is to take 77,300 sq ft in the block, which will be Ireland’s tallest office building.
A fintech firm is taking another 35,000 sq ft in the premises, which is now 70% let by agents Savills and CRBE.
The deal for the space in the 17 storey high building is the largest so far this year in the commercial real estate market.
The building was developed by receivers for the National Asset Management Agency, but bought five years ago by a European fund advised by Tristan Capital Partners and local partners SW3 Capital.
The EXO is a number of buildings that was considered by the postal company for its new headquarters.
The company is planning a refurbishment of the GPO, which also houses a post office and Witness History museum.