Mac Grianna was born in Raheny, a suburb in north Dublin, to an Irish-speaking family.
[1][2] He lives on an alpaca farm in County Meath just outside Ashbourne with his husband Terry Gill whom he married in June 2014.
He is a fan of Desperate Housewives and Coronation Street and supports Dublin and Manchester United.
[4] Mac Grianna was considered a favourite to replace iconic newsreader Anne Doyle when she retired on 25 December 2011.
The presenter did not realise the cameras were rolling after a technical error meant that footage of Mac Grianna readying himself for the broadcast was shown instead of the title sequence.