North Yorkshire Fire and Rescue service were called at 4pm to Barden Moor, between Bolton Abbey and Skipton.
Images on Twitter from Harrogate and Craven districts Watch Manager Martyn Hughes show firefighters and an all-terrain vehicle trying to put the fire out.
Crews from Skipton, Harrogate and Boroughbridge are in attendance.
-> Police hunt suspects after ANOTHER fire breaks out on Yorkshire moorlandNorth Yorkshire Police are also in attendance.
They said no one is believed to have been injured and the A59 is not affected, but urged people to avoid the area if possible.
The cause of the fire, covering around four hectares, is being investigated.
-> Man charged with arson after Ilkley Moor fireIt comes as several fires have broken out - including some deliberately - across Yorkshire moorland over the bank holiday weekend.
Fires at Ilkley Moor are now under control but firefighters were still tackling a blaze on moorland near Meltham -believed to have been started deliberately - on Tuesday afternoon.