A sheathed syringe assembly including a syringe having a cylindrical body provided with a needle at one end thereof and a plunger slideably disposed within said cylindrical body for aspirating or dispensing substances into or from the cylindrical body. A sheath assembly comprised of inner and outer tubular members is attached to the cylindrical body. The inner tubular member is telescopically received in the outer member for reciprocal movement therein between a retracted position exposing said needle and an extended position covering said needle to prevent accidental needle stick. The sheath assembly is provided with a ratchet means for manually advancing said inner tubular member into the extended position with the same hand holding said syringe assembly.