The snake is described as being about 5 feet 6 inches tall, long and is black in colour with yellow bands about every 3 inches along its body.
Police Scotland say the snake is not classed as venomous and poses no threat to the public. It is likely to move towards heat.
Constable Hayley Buchanan said: “Anyone coming across the snake should call Police Scotland at Stranraer on 101. The snake is slow moving and has a distinctive yellow dot between its eyes.”