A protective assembly includes a body for receiving the syringe; and a coupling device inside the body, rigidly connected to the barrel as regards to axial movement relative to the body. The coupling device includes an attaching element which can be either in an engaged state to axially fix the coupling device and the plunger rod, or in a release state in which the coupling device and the plunger rod are axially free relative to one another. The coupling device is axially movable in the body from a storage position to an injection position in which the needle extends beyond the body, and in which the attaching element can move towards the release state. The coupling device is axially movable in the body from the injection position towards a safety position, in which the needle is covered by the body.