CD28 molecule (CD28), cytotoxic T-lymphocyte-associated protein 4 (CTLA4) and inducible T-cell co-stimulator (ICOS) are important regulators of the immune system. Vitiligo, a common autoimmune skin disorder, is characterized by a loss of melanocytes that results in cutaneous white patches. The aim of the present study was to determine whether or not polymorphisms of the CD28, CTLA4 and ICOS genes are associated with non-segmental vitiligo in a Korean population. To determine the relationships between CD28, CTLA4 and ICOS genes and vitiligo, four single nucleotide polymorphisms (SNPs) associated with the CD28 gene [rs1879877 (promoter, -1198), rs3181097 (promoter, -1059), rs2140148 (intron 1) and rs3116494 (intron 2)], two SNPs associated with the CTLA4 gene [rs231777 (intron 1) and rs231779 (intron 1)] and five SNPs associated with the ICOS gene [rs4270326 (intron 3), rs11571314 (intron 3), rs10183087 (3' untranslated region; UTR), rs4404254 (3'UTR) and rs1559931 (3'UTR)] were selected. Two hundred and thirty-one patients with non-segmental vitiligo (NSV) and 405 healthy controls were enrolled. Genotyping was performed using the restriction fragment length polymorphism technique and direct sequencing. SNPStats, Haploview 4.2 and SPSS 18.0 were used to conduct the analyses. Significant differences were noted between CTLA4 (p<0.05) and NSV, but not CD28 and ICOS (p>0.05). However, these associations disappeared after Bonferroni correction. The CD28, CTLA4 and ICOS genes may not be associated with NSV.