Background Topical tacrolimus has been used for vitiligo as a common treatment option for more than ten years while the underlying mechanism is still uncertain.The aim of this study was to investigate the direct effects of tacrolimus on the melanogenesis and migration on human A375 melanoma cells.The expression of c-KIT mRNA and protein of human A375 cells were also investigated.Methods The cultured A375 human melanoma cells were randomly assigned to control and tacrolimus treatment groups (10,102,103and 104 nmol/L).The cell proliferation was measured with Cell Counting Kit-8 assays.Melanin content was measured with NaOH method.Transwell migration assay was used to measure cell migration.The expression of c-KIT mRNA and protein were measured with real-time fluorescence quantitative polymerase chain reaction and immunohistochemistry respectively.Results The cell proliferation of the 103 and 104 nmol/L tacrolimus groups were significantly lower (0.666±0.062 and 0.496±0.038) as compared with the control (0.841±0.110,P ＜0.05).The mean melanin content in all groups treated with different concentration of tacrolimus (10,102,103,104 nmol/L) increased compared with the control group (P ＜0.05).Dosedependent increase in cell migration were seen in all tacrolimus-treated groups (P ＜0.01).The expression of c-KIT mRNA level in A375 cells exposed to tacrolimus (103and 104 nmol/L) had significantly increased by 3.03-fold and 3.19-fold respectively compared with the control (P ＜0.05).Conclusions Although tacrolimus had no effects on cell proliferation on A375 human melanoma cells,it could increase the melanin content and cell migration.The expression of c-KIT mRNA and protein increased dose-dependently in tacrolimus-treated groups as compared with the control.Our study demonstrated that tacrolimus could enhance the melanogenesis and cell migration on A375 cells.