A syringe having a bonded needle, comprising a syringe body, a needle protector comprising a flexible cap, an outer sleeve, which can move along a longitudinal axis between an extended position, in which it covers the needle, and a retracted position, in which it does not cover the needle, and a collar, which is mounted with a radial clearance around an end part of the syringe body and which comprises at least one pin engaged in a guide opening of the sleeve. A portion of the flexible cap fills the radial clearance between the end part of the syringe body and the collar when the cap is mounted on the syringe, such that the collar cannot rotate around the end part of the syringe body as long as the cap is mounted on the syringe.