Endothelial cell proliferation is a hallmark of angiogenesis and plays a key role in the process of tissue repair. Low-intensity (670 nm) laser irradiation influences endothelial cell proliferation in vitro. Light in the near infrared spectrum may have clinical applications in erectile dysfunction. The purpose of this study was to investigate the effects of irradiation with light-emitting diodes (LEDs) at different wavelengths on human vascular endothelial cells in vitro. Human umbilical vein endothelial cells (HUVECs) were irradiated with LEDs at 410, 480, 595, and 630 nm in doses of 1, 2.5, 5, and 10 J/cm2. After 24 h of LED irradiation, effects on cell viability, nitric oxide (NO) secretion, and eNOS expression were assessed by using cell viability assays, Western blot, and real time-polymerase chain reaction, respectively. The cell viability assay demonstrated that irradiation with LEDs at 630 nm significantly increased the proliferation of HUVECs. In addition, irradiation with LEDs at 630 nm was more effective in stimulating NO secretion and eNOS expression from HUVECs than irradiation with LEDs at 410, 480, and 595 nm. Irradiation with LEDs at 630 nm was effective for inducing cell proliferation, NO secretion, and eNOS expression in HUVECs. These results suggest that irradiation with LEDs at 630 nm may be a therapeutic strategy for vasculogenic erectile dysfunction.