This study investigates the operation of Active Chilled Beam under cooling operation in single occupant office in a high-performance LEED Gold Building at the British Columbia Institute of Technology in Vancouver. The thermo-fluid phenomena of room air were studied inside a few offices under cooling operation in stable room temperature conditions. Active Chilled Beams were found performing effectively in cooling mode operation. Surface temperature distribution and the air temperature distribution in the occupied zone were found uniform at all heights and close to the room setpoint. The air velocities were within the recommended air velocity set by ASHRAE Standard for thermal comfort except at the colliding jet between two beams in some offices. The operative temperature measured near the occupant was found close to the room setpoint. The supply air velocity and supply air temperature at both the slots of the beam were found different. It was concluded that the difference in supply air velocity could be due to the uneven pressure distribution in the primary air plenum owing to the connection method of the duct to the primary plenum and the difference in temperature could be due to the circuit arrangement of heat exchanger inside the Active Chilled Beam, which needs further research and investigation of the beam characteristics in a controlled environment.