Gardai have advised people to stay away from Bray Head as firefighters continue to tackle the blaze that has so far caused "significant damage".
Firefighters remained on the mountain all night although the fire does not pose a threat to property and no injuries have been reported.
A previous fire last week already burned a considerable area of Bray Head.
WICKLOW: Gardai continue to advise people to avoid Bray Head due to last night's fire. Visibility may been affected. https://t.co/qvBPcgxUj8— AA Roadwatch (@aaroadwatch) August 17, 2016