The Taoiseach said yesterday he would be raising the Dublin murder of Joseph Rafferty with Sinn Féin leader Gerry Adams at their next meeting.
Mr Rafferty's family say the 29-year-old father of one was shot dead by alleged IRA members outside his apartment in west Dublin in April.
Family members travelled to Belfast earlier this month to meet the sisters of Robert McCartney as part of their campaign for justice.
They believe Sinn Féin is protecting his killers, but the party has condemned the murder and strongly denied any links.
Mr Ahern yesterday met Mr Rafferty's two sisters, Esther Uzell and Sandra Little, along with their local Fianna Fáil councillor, Garry Keegan, for 45 minutes at Government Buildings.
Yesterday Mr Adams repeated Sinn Féin denials of any republican involvement, saying that a criminal element was responsible.
Mr Keegan said afterwards: "Mr Ahern said that he had followed the publicity of the case very carefully over the last number of weeks. He said he would definitely bring up the issue at the next meeting with Gerry Adams."
Ms Uzell said afterwards that Mr Ahern had said he was "disgusted" by the murder and assured her of his support.
"I just told him the story from beginning to end of exactly what happened to Joseph, and Mr Ahern has given us his full support," she said.
Mr Ahern said of the Rafferty family: "They've had a very, very difficult time, and we have to see what way we can help them.
"The Garda investigations are going on, and obviously security and intelligence work is also going on."
Mr Keegan added: "It's not a campaign to get at Sinn Féin or the IRA. It's a fight for justice and we're calling on Sinn Féin-IRA to hand over the people responsible.
"Just like the McCartney case, the publicity surrounding this case won't go away until somebody is brought to justice."
Mr Rafferty died after being shot twice in the upper body as he left his apartment at the Ongar Park housing estate in Blanchardstown last April.
The shooting is believed to have followed a minor dispute during a party in October 2004.
The Rafferty family claim they have been the victims of alleged IRA intimidation in their south inner-city neighbourhood.
Earlier this month Dublin City Council unanimously backed a Keegan motion for an immediate end to the intimidation of the Rafferty family.
Cllr Keegan promised that more public events would take place in coming days to keep the family's plight in the spotlight.