The man – who has been named locally as David Gavin – was last seen diving off a bridge in British Columbia, Canada but failed to surface.
Mr Gavin is originally from Castlebar, Co Mayo and is said to have only moved to Canada a few months ago for work.
The Royal Canadian Mounted Police (RCMP) have said they received a report of the incident after 3.30pm on Friday and a search and rescue operation was immediately launched in the Kinbasket Lake area.
The Calgary Herald reports that two boats and a dog were involved in the search over the weekend and the E Division Underwater Recovery team is also set to be deployed.
Police have contacted the man’s family, who are set to arrive in Canada today.
His parents both work for Mayo County Council and the family are said to be well-known and well-liked.
Mr Gavin was a member of Breaffy GAA.
Councillor Michael Kilcoyne said his thoughts are with them at this difficult time.
He told Independent.ie: “I’m very saddened to hear the news.
“It’s a terrible time for the family, this is every parent’s nightmare.”
The Department of Foreign Affairs said in a statement: “The department is aware of an incident in British Columbia involving an Irish citizen.
“Our Embassy in Ottawa is liaising closely with the local authorities and the department is providing consular assistance in this case.”