Large heath fire near Littlesea between Studland and the Sandbanks Ferry.
Over 90 firefighters were fighting the fire at its peak.
The fire is believed to have been caused by a barbecue or campfire.
The fire service posted: We have found evidence of a campfire and BBQ at the seat of the fire on #Studland and believe this to be the cause of the fire which started yesterday. Please DO NOT have campfires, bonfires or use barbecues in the countryside.