The confidential freephone line, which was recommended by the Garda Inspectorate five years ago, will be operated by the Command and Control Centre at Harcourt Square, which deals with 999 calls.
Trained civilian and garda staff at the centre will refer calls to the Protected Services Bureau for evaluation and investigation.
The PSB consists of a range of dedicated sections, including a National Child Protection Unit.
This unit is due to second a social worker from the Child and Family Agency to work with it and ensure proper communication with Tusla.
Temporary phonelines for child sex abuse victims were set up in the wake of official inquiries into Ferns, the Dublin Archdiocese and the Diocese of Cloyne.
In its report, Responding to Child Sexual Abuse, published in February 2012, the Garda Inspectorate recommended that a 24/7 phoneline be set up for the reporting of allegations of child sexual abuse and called for automated answer lines to be discontinued.
In a progress report the following year, the inspectorate said the gardaí had stated they would install the dedicated phone line in Command and Control by the fourth quarter of 2013.
The inspectorate also recommended that only specially trained gardaí should take statements from alleged child sex abuse victims — a recommendation repeated in its 2014 Crime Investigation report.
Senior Garda management came under pressure last week at a public meeting with the Policing Authority as to how many specialist child interviewers they had.
Deputy Commissioner John Twomey said there were 73, but this was disputed by authority member Dr Vicky Conway.
She said figures she was supplied with by the gardaí last January indicated that the number who had completed training was in “single figures”, though larger numbers were in training.