Objectives : Nickel is a major metal used in the nickel-chromium alloys of most orthodontic appliances, partial denture and implants. This study was carried out for the examination of the cytotoxicity on nickel sulfide in cultured NIH3T3 fibroblasts, and poncirin effect on nickel-induced cytotoxicity. Methods : Cell viability for the MTT assay and cell adhesion activity for the XTT assay. Results : The $IC_{50}$ of nickel sulfide by the MTT assay was $93.7;{mu}M$. Poncirin was significantly increased the cell viability and cell adhesion activity. Conclusion : Nickel was highly toxic and poncirin has the inhibitory effects against nickel induced cytotoxicity.