The Irish Society for the Prevention of Cruelty to Children has said the over 45,000 calls its Childline service answers at night will go unanswered next year, unless the public provides additional funds.
The charity has issued an appeal for €1.2m to keep the 24-hour service open.
It says 11% of its calls are to the night-time service, which has become "a critical support to children in distress", who in many instances are prevented by domestic circumstances from phoning at other times of the day.
The ISPCC's interim CEO, Caroline O'Sullivan, said it had issued the emergency appeal because Childline is the only support option available to many children.
She said the loss of the night service would have a huge impact on those in real need.
Ms O'Sullivan said that if Childline cannot continue to provide a 24-hour service some children will be forced into silence and only a generous response to the appeal can stop this from happening now.
Childline has been operating in Ireland for 26 years and is funded almost exclusively on public donations.
The night-time service has grown over the past 15 years.
The service says that so far this year, issues of abuse, personal welfare and mental health accounted for over 21% of calls it answered.