Abstract: A syringe assembly has a safety sheath to prevent accidental pricking of the user after injecting fluid from the syringe into an injection site of a patient. The syringe assembly includes a body, a needle, and a slidable plunger. A tube is slidably mounted on the rear end of the plunger and has a thumb tab for pushing the plunger forwardly in the syringe body. The syringe body extends through a protective sheath. After the fluid is injected from the syringe body into the patient, the user pulls rearwardly on the finger flange so as to force the plunger into the tube and thereby pull the needle into the sheath, as the needle is being withdrawn from the patient. The needle is automatically enclosed by the sheath using only one hand and without gripping the sheath.