Dublin fire services have received 500 calls and attended 130 incidents ranging from bonfires to a number of cars being burnt out in the Tallaght area.
In one of the most serious incidents, a 12-year-old boy sustained serious facial injuries due to a firework.
It is understood the boy is now in a stable condition at Tallaght Hospital.
The Dublin Fire Brigades Ambulance Service has responded to 85 calls.
Some were drug and alcohol related, while others were for minor issues.
It has also been reported that an ambulance was stoned by a group of youths as it returned to Beaumont Hospital with a patient.
In terms of the other 11 counties monitored by Tara Street, including Meath, Louth, Cavan, Monaghan and Kilkenny, 250 calls have been received and 70 incidents attended.
None of those incidents have been described as serious.
The busiest period for the emergency services on Hallowe'en night is between 9pm and 2am.