A modular floor terminal basket with a damper is mounted in the floor of an occupied space for delivering air from an under floor air plenum to the occupied space above. The modular floor terminal basket with a damper includes a generally cylindrical basket with air inlet openings on the basket side and an air outlet at the top of the basket. A damper is positioned in the basket for movement from a lower opened position to an upper closed position. The position of the damper is controlled by an actuator which in turn is controlled by a thermostat/controller in the occupied space above the floor. The damper is slideably mounted on a damper guide extending from the bottom of the basket toward the air outlet at the top of the basket. The actuator rotates a threaded shaft that engages a threaded collar attached to the damper so that the damper slides up and down along the damper guide.