Although chronic obstructive pulmonary disease (COPD) is an inflammatory disease predominantly involving T cells, no study ofRhodiolaas an immunomodulator in COPD patients has been reported. In this study, COPD patients tookRhodiola crenulata500 mg (n= 38) or placebo (starch/phosphate buffered saline) (n= 19) daily for 12 weeks and were compared with untreated, age-matched, and sex-matched non-COPD control subjects. Our results showed that serum levels of IL-2, IL-10, and IFN-γ in COPD patients before treatment are significantly higher than levels in non-COPD controls (p< 0.05). A significant decrease in IFN-γ was seen in theRhodiolatreatment group (p< 0.05) but not in the placebo group (p> 0.05). The results suggested thatRhodiolatreatment had beneficial antiinflammation effects, lower COPD assessment test score and decreased high-sensitivity C-reactive protein, on COPD patients (p< 0.05). The effects ofRhodiolatreatment on COPD patients were shown to decrease the IFN-γ concentration and CD8+ count but increase the expressions of CD4+CD25+FOXP3+ and CD4+CD25+CD45+FOXP3+ in the blood significantly (p< 0.05). This is the first trial usingRhodiolaas a complementary therapy for COPD patients. T cells play an important role in the pathogenesis of COPD through the increased expression of CD8+ T cells and IFN-γ and may be a viable target for potential therapy. Copyright © 2014 John Wiley & Sons, Ltd.