The invention relates to a safe support device for a syringe, said support comprising a support sheath for the body of a syringe, and safety means which comprise an inner sheath suitable for sliding relative to said support sheath between a waiting retracted position, in which said inner sheath is substantially retracted inside said support sheath, and an active protection position, in which said inner sheath projects from said support sheath. The inner sheath has a free end portion formed by a flexible end-piece. The invention also relates to an assembly comprising such a safe support device and a syringe having a body, a piston and a needle disposed at one end of said body.