In a statement, Cork Opera House said its interim chief executive officer, Padraic Liston, had led an internal investigation into the matter.
It was claimed the alleged fraud was perpetrated over the last 15 months.
During the investigation, a member of staff had been interviewed, the company said.
“The employee, following an appropriate disciplinary process, has been removed from his employment,” a statement said.
Cork Opera House chairman Damian Wallace said the board was very disappointed to learn of the suspected fraud and had immediately informed the Gardaí and all stakeholders.
He confirmed the matter was under Garda investigation.
According to the board, the reported sum at the centre of the investigation was in the region of €63,000.
Cork Opera House board also said a review of current internal controls was progressing and it was likely to implement new checking procedures which would eliminate future exposure to fraud.
The board emphasised the alleged fraud was not related to recent financial difficulties at the Opera House, although the matter had contributed to the current year loss.
The board acknowledged, however, the incident will add to the challenges currently facing the venue.
Cork Opera House had, earlier this year, decided to close for the summer to save money after suffering losses last year of more than €300,000.
The losses were posted almost 12 months after the theatre had undergone a €2 million refurbishment.
The refurbishment had involved the installation of new seating and had been paid for following some fundraising by the Opera House on top of grants from Cork City Council and the Department of Arts, Sports and Tourism.