John McCann, chief executive of UTV Media, said: "This acquisition enables our multimedia offering throughout Ireland to take a significant step forward and firmly reflects UTV Media's strategy of creating a diversified media business in the UK and Ireland.
"FM104 is the market leader in Dublin and we look forward to developing this position within UTV."
Communicorp, owned by Irish billionaire Denis O'Brien, was forced to sell FM104 after the Broadcasting Commission of Ireland did not approve the station's sale to Communicorp from the previous owner, Emap.
Emap had sold its three Irish radio stations -- FM104, Donegal's Highland Radio and national station Today FM -- for £135.5m to Communicorp, but only the latter two were cleared by the commission.
The commission said Communicorp, which owns another Dublin station 98FM and a national station Newstalk, might have an "undue amount of communications media in Dublin" if it bought FM104.
Emap sold its consumer magazine and radio divisions to H Bauer for £1.14bn earlier this month and a condition of the sale was the completion of the disposal of the Irish stations.
Assuming the Irish regulator clears the sale of FM104 to UTV, it will not fall back into Emap's hands, meeting the condition of the Bauer sale.