Background: Light emitting diode (LED) is recently used in variable conditions to stimulate wound healing, skin restoring and hair growth. Previously, we showed that LED irradiation upregulated the hair growth related factors in dermal papilla cells (DPCs) and the irradiation with certain wavelength improved the skin lesion of atopic dermatitis in a mouse model. Objectives: We aimed to determine the effect of LED irradiation on the interferon (IFN) gamma-treated dermal papilla cells and H₂O₂-induced fibroblast cells (FBCs). Methods: DPCs were exposed to LED irradiation with a wavelength of 475, 500, 505nm and a dosage of 10 J/㎠. FBCs were exposed to LED irradiation with a wavelength of 415, 475, 515nm and a dosage of 10 J/㎠. Cell proliferation was examined using MTT assay and Wnt/β-catenin pathway and apoptosis related genes (p53, pRb, Bcl2, and Bax) were measured by real-time PCR and western blot assay. Results: The LED irradiation significantly promoted cell proliferation. Furthermore, LED irradiation at 505nm upregulated Wnt5a and β-catenin expressions remarkably and suppressed IFN receptor in DPCs. Also, LED irradiation significantly downregulated the H₂O₂ induced-expression of p53 and p21 in FBCs. And LED irradiation at 515nm upregulated Bcl2 and suppressed Bax expression in H₂O₂-induced FBCs. Conclusion: We found that LED irradiation, especially green light, has therapeutic potential to treat hair loss and skin aging in vitro and it was mediated via Wnt/βcatenin pathway.