β-Glucan, derived from Saccharomyces cerevisiae, is a biological response modifier which affects the innate and adaptive immune responses. The CCR5 chemokine receptor is crucial for immune cell responses. In this study, the effects of the carboxymethylated form of β-glucan (CM-G) on the lymphocyte population of CCR5 genotype patients with prostate cancer (PCa), undergoing androgen deprivation therapy (ADT) was assessed. The CCR5 genotype and lymphocyte population was investigated by cytometry flow in 30 Brazilian patients with advanced PCa who were treated with CM-G for 28 days. The analysis of the CCR5 chemokine receptor revealed that the wild-type genotype Wt/Wt was present in 80% of patients, while the heterozygotic genotype Wt/delta32 was present in 20% of patients. After CM-G administration, a significant increase in CD3(+), CD4(+) and CD8(+) T lymphocytes was observed in patients who displayed the wild-type genotype for the CCR5 chemokine receptor. No association was found between patient's age or length of ADT and increase in T lymphocyte cells. The results demonstrated the ability of CM-G to stimulate CD4(+) and CD8(+) T cells in the peripheral blood of patients carrying a wild-type CCR5 genotype, suggesting an interaction between immunomodulation by CM-G and the CCR5 receptor.