Interleukin-7 (IL-7) is a critical factor in maintaining or inducing effective antiviral CD4+ and CD8+ T-cell responses. The aim of this study was to examine the association of interleukin-7 receptor-α (IL7RA) polymorphisms with a sustained virologic response (SVR) after hepatitis C virus (HCV) therapy with pegylated interferon-alpha plus ribavirin (pegIFNα/ribavirin) in 177 human immunodeficiency virus (HIV)/HCV-coinfected patients. We performed a retrospective study in 177 naïve patients who started HCV treatment. The IL7RA rs6897932, rs987106, and rs3194051 polymorphisms were genotyped by the GoldenGate® assay. An SVR was defined as undetectable HCV viral load through 24 weeks after the end of HCV treatment. The highest SVR rate was found in patients with the rs6897932 CC (p = 0.029) and rs3194051 GG (p = 0.002) genotypes, and HCV genotypes 2/3 (GT2/3) infected patients with the rs987106 AA genotype (p = 0.048). Additionally, carriers of the rs3194051 GG genotype had a higher likelihood of achieving an SVR [adjusted odds ratio (aOR) = 5.32; 95 % confidence interval (CI) = 1.07-26.94; p = 0.040] than patients with the rs3194051 AA/AG genotype, while rs6897932 CC (aOR = 0.63; p = 0.205) and rs987106 AA (aOR = 0.60; p = 0.213) were not significant. Moreover, three major haplotypes were found: 46.6 % for CTA, 32.4 % for CAG, and 20.7 % for TAA haplotypes. Patients infected with GT2/3 and carriers of the CTA haplotype had lower odds of achieving an SVR (aOR = 0.08; p = 0.004) and the CAG haplotype (favorable alleles) had higher odds of achieving an SVR than other haplotypes (aOR = 21.96; p < 0.001). IL7RA polymorphisms seem to play a significant role in the virological response to pegIFNα/ribavirin therapy in HIV/HCV-coinfected patients, in particular among patients infected with HCV GT2/3.