Objective To detect the frequencies of peripheral programmed death-1+ (PD-1+) lymphocytes and CD4+CD25+FOXP3+ regulatory T cells in patients with gastric adenocarcinoma. Methods The study enrolled 29 patients with gastric adenocarcinoma and 29 age- and sex-matched healthy controls. Frequencies of PD-1+ lymphocytes and CD4+CD25+FOXP3+ regulatory T cells were detected using flow cytometry. Results The number of PD-1+ lymphocytes and CD4+CD25+FOXP3+ regulatory T cells in peripheral blood was higher in patients with gastric adenocarcinoma than that in the control group. Moreover, linear correlation analysis indicated a positive correlation between PD-1 expression and frequency of CD4+CD25+FOXP3+ regulatory T cells in peripheral blood of the patients. Conclusion Gastric adenocarcinoma patients present with increased PD-1+ lymphocytes and CD4+CD25+FOXP3+ regulatory T cells in the peripheral blood.