This study investigated whether the single nucleotide polymorphisms (SNPs) and haplotypes of interleukin-10 (IL-10) were associated with cachexia in 223 Chinese patients with gastric cancer diagnosed by histopathological examination. Genomic DNA was extracted from peripheral blood leukocytes. The SNPs at positions -1082A/G, -819T/C, and -592A/C in the IL-10 gene promoter were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). No significant differences were found in the allele and genotype frequencies of -592A/C in patients with or without cachexia. Increased frequency of the -1082G allele was found in patients with cachexia (OR = 1.83, 95% CI, 1.00-3.33, p = 0.049). In a logistic regression analysis adjusted for body weight, carcinoma location, and stage, the -1082AG genotype was associated with an odds ratio of 1.989 (95% CI, 1.041-3.802, p = 0.037) for cachexia. The -819CC genotype was associated with an odds ratio of 3.393 (95% CI, 1.298-8.871, p = 0.013) for cachexia. Furthermore, haplotype analysis revealed that the G(1082)C(819)C(592) haplotype was associated with increased risk of cachexia as compared to the A(1082)T(819)A(592) haplotype (OR = 2.21; 95% CI, 1.14 - 4.30; p = 0.02). Our results suggest that genetic polymorphisms of IL-10 contribute to the susceptibility to cachexia in patients with gastric cancer in the Chinese population.