Abstract: A thread monitor particularly for a sewing machine having a needle, the monitor comprising a control device operable for stopping the operation of the machine, a thread feeler engageable with the thread supplied to the needle, and a bracket mounting the feeler for movement between a retracted position with respect to the control device and an operative position for actuating the control device for stopping the operation of the machine. The feeler is biased toward its operative position, the bias being greater than the frictional force present between the feeler and its mounting as the machine vibrates during the operation thereof but less than the frictional force present between the feeler and its mounting when the machine is not in operation, so that, upon thread breakage when the machine is in operation, the feeler will move to its operative position for stopping the operation of the machine and, when the machine is not in operation, the feeler remains in retracted position.