This article examines the combined effects of ultraviolet (UV) radiation, elevated temperature and humidity on the mechanical properties of the pile pipe made of polymer-composite materials (PCM) based on polyester resin reinforced with basalt fiber and manufactured by the wet winding method. It is shown that UV radiation is one of the significant factors affecting the performance of PCM piles. Long-term exposure to UV radiation leads to a decrease in the strength properties and deformation capacity of PCM. Thus, a 20% decrease in strength properties occurs with UV exposure for 6100 hours. The cause of degradation of the mechanical properties of PCM under the influence of UV radiation is extensive surface erosion, leading to microcracking of the polyester base of the PCM with the subsequent formation of surface and subsurface pores.