A syringe and needle assembly includes an elongated hollow barrel, a needle unit, and a plunger assembly. The hollow barrel has a connecting portion. The needle unit is disposed at the connecting portion and has an engaging structure, and the engaging structure is located in the hollow barrel. A plunger rod of the plunger assembly is movably disposed in the hollow barrel and has a pushing portion and an operating portion formed in front and rear ends of the plunger rod respectively, and the pushing portion faces the connecting portion and has a plurality of elastic hooks. The plunger assembly is adapted to move towards the connecting portion to push a liquid in the hollow barrel to be injected through a needle of the needle unit, and the plunger assembly is adapted to keep moving towards the connecting portion, such that the elastic hooks are engaged with the engaging structure.
