A pneumatic pinch valve having a main body, a piston supporting a plunger, and a detachable headpiece for receiving a portion of compressible tubing between the plunger and a contoured surface of the headpiece is disclosed. A first safety cap which may restrict access to the plunger when the valve is operated and a manual override handle which may open the plunger are also provided. The pneumatic pinch valve is opened by the injection of gas through an air inlet port to a pneumatic chamber. The headpiece and plunger are configured to compress a portion of flexible tubing in a manner which reduces or eliminates damage to the tubing even after repeated open/close cycles. Further, the pinch valve may be installed onto an existing process system without disruption of fluid flow. Also disclosed is a manual version of the pinch valve.