Galway West TD Mr Noel Grealish has replaced Senator John Minihan as chairman of the Progressive Democrats parliamentary party.
Mr Minihan had stepped down after a year in the post in line with party policy, a spokesman for the Tánaiste, Ms Harney, told The Irish Times last night.
Mr Grealish was unanimously chosen at the weekly parliamentary party meeting.
"I am very much looking forward to the challenges ahead," he said.
The annual changeover offers the opportunity to the PDs, with eight TDs and three senators, to increase the profile of lesser-known members.
Mr Grealish was one of three Progressive Democrats candidates to run in Galway West after the resignation of one of the party's founders, former minister of state Mr Bobby Molloy.
Mr Grealish won a third of the quota on the first count, but the party managed to ensure he got enough transfers to take the last of five seats on the 16th count.
Following the announcement by Dublin South TD Ms Liz O'Donnell that she did not want to return as minister of state, it was believed for a time that Mr Grealish could replace her.
However, Limerick East TD Mr Tim O'Malley, who serves in the Department of Health and Children, took the final promotion slot enjoyed by the Progressive Democrats.