This study was performed to evaluate the potential association between serum heavy metal levels and lung function in a cohort of chronic obstructive pulmonary disease (COPD) patients. We analyzed data from 152 subjects enrolled in a cohort study on COPD from 2012 to 2013 and living in a dusty area. In total, 152 subjects from the cohort study were enrolled; 111 were diagnosed with OLD. There was a significant association between post-bronchodilator FEV1 and serum mercury level after adjusting for age, gender and smoking status (p=0.03). Following the adjustment, a significantly higher prevalence of OLD was observed in subjects in the highest mercury concentration tertile (p=0.03). The risk of OLD was significantly higher for subjects in the higher mercury concentration (odds ratio, 3.62; 95% confidence interval: 1.29-10.18) than in those in the lowest tertile. In conclusion, serum mercury level may be a risk factor for reduced lung function and OLD.