In a device for protecting a work spindle (2) that is rotatably supported in a spindle head (4A, 4B) of a processing machine and/or a tool (3) clamped in the work spindle (2) from collisions with obstacles in the processing chamber (1) of the processing machine, a plurality of distance sensor modules (6) are arranged on or in a spindle nose (4B) that forms the termination of the spindle head (4A, 4B) toward the processing chamber (1) such that they point toward the processing chamber (1) and are connected to a common signal processing unit (8). When an obstacle is present in a predetermined area of the processing chamber (1), this signal processing unit generates a warning signal based on the measuring signals delivered by the individual distance sensor modules (6). An output (15) of the signal processing unit, at which the warning signal is generated, is connected to the machine control (16) of the processing machine. The distance sensor modules (6) preferably consist of radar or ultrasonic sensor modules.