The support group One in Four has said some people are waiting more than eight months for psychotherapy.
In its annual review for 2022, the charity said it supported 753 men and women who had experienced sexual abuse in childhood.
It also supported 56 men who had caused sexual harm to children.
The charity said it delivered individual and group psychotherapy sessions to 172 clients, and met 94 people for a first assessment.
"We believe that survivors deserve access to expert services in a timely way when they reach out for support," it said.
"Sadly, the demand for psychotherapy services always exceeds our ability to respond immediately."
One in Four said its waiting list for psychotherapy on December 31st was 83 - a waiting time of eight and a half months.
The group was supported by Tusla to create a new position of Waiting List Case Manager, who provided support and crisis counselling to people on the list.
The charity said 41% of its clients were abused in their own family, while 43% of the clients were men.
Eight families also attended its family support programme.
The Government is being called on to increase funding supports for sexual abuse survivors in Ireland.
'Incidence may be increasing'
One in Four CEO Maeve Lewis said more assistance is badly needed.
"People [who] reach out to us are often in great distress, they're in crisis," she said.
"This would be the case across all the services working with sexual abuse and sexual violence.
"It really, really needs resourcing so that when people reach out they will be given access to an expert service in a very timely manner.
"Research that was published this year by the CSO found that there still is a stubbornly high level of of child sexual abuse in abuse in Ireland.
"In their research, the highest prevalence was among people aged 18 to 24 years.
"That's suggesting that in fact the incidence is not going down and in fact may be increasing," she added.
