Conradh na Gaeilge
In the 1980s and 1990s, Mac Stíofáin became active in the Irish-language organisation Conradh na Gaeilge. At that organisation's centenary celebration held in Dublin's O'Connell Street in 1993, he was a guest of honour on the platform. He remained a member of the standing committee ("Coiste Gnó") of Conradh na Gaeilge until his death. He lived in the Meath Gaeltacht. Visitors to his home were greeted at the front door with a mat saying "Labhair Gaeilge Anseo" ("Speak Irish here").