We have investigated the influence of various plasma treatments of electrospun polycaprolactone (PCL) scaffolds on the adhesion and proliferation of human umbilical endothelial cells (HUVEC). The PCL scaffolds were treated in plasmas created in O-2, NH3 or SO2 gas at identical conditions. Surface functionalization of plasma-treated samples was determined using X-ray photoelectron spectroscopy. Cell adhesion and morphology were investigated by scanning electron microscopy and the influence of plasma treatment on cell adhesion and viability was evaluated with cell viability assay (MTT assay). The results showed the highest metabolic activity of HUVEC on PCL samples treated with O-2 and NH3 plasma. Accordingly, the cells reflected the best adhesion and morphology on O-2 and NH3 plasma-treated PCL samples already at 3 h. Moreover, treatment with O-2 and NH3 plasma even stimulated endothelial cell proliferation on PCL surfaces by 60% as measured at 24 h, showing significant improvement in endothelialization of this material. Contrarily, SO2 plasma appeared to be less promising in comparison with O-2 and NH3 plasma; however, it was still better than without any plasma treatment. Thus, our results importantly contribute to the biocompatibility improvement of the PCL polymer, commonly used for scaffolds in tissue engineering.