It starts on the A75 at Halfway House, to the west of Kirkcowan. The road heads east through a wood and quickly reaches Kirkcowan itself. It goes round two sides of the white-painted church before heading south along Main Street, meeting the B735 en route. After leaving the village the road zigzags to cross a narrow bridge over the River Tarff.
The road follows the river valley downstream for over a mile before meeting the B7052, after which it crosses a narrow bridge over the River Bladnoch to go through Spittal. It continues southeastwards across Torhousemuir. This is quite low - but does consist of a number of hills which the road has to avoid.
Presently the B733 reaches a crossroads where it has to give way to the B7005. The road now narrows and climbs to enter Wigtown. It runs along the High Street to end on the A714, where that road has to TOTSO.