St Patrick's Mental Health Services has confirmed it has received an official complaint in relation to Al Porter.
The hospital is now investigating the complaint against the comedian and former Today FM presenter.
Last weekend, The Sunday Times reported allegations of inappropriate behaviour made against Al Porter while engaging in an awareness-raising event at the organisation.
In a statement issued on Sunday, the hospital had said that "no allegations, complaints or concerns had been made to SPMHS by service users or staff in respect of Mr Porter".
In an updated statement this evening, St Patrick's says: "Since issuing that press release, SPMHS has received such a complaint. The organisation is currently investigating the complaint in line with its policies and procedures.
"There will not be any further press releases or statements by SPMHS regarding this matter until that investigation is complete."
Over the weekend, Mr Porter resigned from his lunchtime show on Today FM amid allegations of inappropriate behaviour.
He has also stood aside from this year's pantomime in Dublin's Olympia Theatre, in which he had been due to star.
A statement issued by the comedian on Sunday said he apologised to anyone he may have genuinely offended.
He added that he will be taking some "time away from the spotlight".
— Al Porter (@TheAlPorter) November 19, 2017