The new chairman of the Fine Gael parliamentary party is Limerick West TD Dan Neville.
He succeeds Charlie Flanagan, who was appointed to Cabinet last week.
Mr Neville, 67, has been a long-term champion of the campaign against suicide.
He defeated Waterford TD Paudie Coffey whose candidacy was seen as having the backing of the party leadership.
Mr Neville was first elected to the Dáil in 1997 after serving as a Senator on the Labour panel since 1989.
He was appointed Fine Gael Spokesperson on Mental Health in 2007 and is currently a member of the Joint Oireachtas Committee on Health and Children.