The polymer pipe joint assembly includes a fitting, positioned inside the polymer pipe, a coupling, having at least one cylindrical section, which covers the pipe and fitting, the assembly having a sleeve capable of changing its geometrical dimensions and shape under pressure. The sleeve has at least one cylindrical section placed between the pipe and coupling, the fitting has a shoulder on its outside surface, restricting the movement of the pipe and sleeve, while the inside surface of the coupling has a lead-in chamfer. The change of the dimensions of the sleeve can be performed both by selecting different types of sleeve material or by its construction.