Fire crews have come under attack from youths throwing fireworks in Coalisland, Northern Ireland Fire and Rescue Service (NIFRS) said.
They also had to withdraw from incidents in Rostrevor and Newry because of hostile crowds on Monday.
There were no reports of any injuries.
NIFRS said it was the busiest Halloween in six years with a 47% rise in the number of calls compared with last year.
Most of the 166 incidents attended by firefighters were started deliberately. Many involved grassland and bonfire materials including tyres.
A total of 232 calls were received from across the region.
An NIFRS spokeswoman said: “This equates to an increase of 47% on incidents attended during Halloween 2015 and represents the busiest Halloween period since 2010 in terms of both calls received and mobilised incidents.”