He was well known for his portrayal of Peadar Ó Conghaile in the long-running soap Ros na Rún.
Ó Neachtain, a native Irish language speaker, was born in Cré Dhubh, An Spidéal, County Galway.
In addition to his work as a television actor, he appeared on stage at Taibhdhearc na Gaillimhe and elsewhere.
[citation needed] Idir Shúgradh agus Dáiríre (In Jest and in Earnest) is an award-nominated 2005 TG4 funded documentary film about Ó Neachtain, made by Mac Dara Ó Curraidhín.
[citation needed] As an active participant in the Gaeltacht Civil Rights Movement, Ó Neachtain helped lay the groundwork for the establishment of Údarás na Gaeltachta and Radió na Gaeltachta.