Chronic obstructive pulmonary disease (COPD) remains a major public health problem with relatively high prevalence rates worldwide (5.0-13.0%). COPD is a major cause of morbidity and mortality worldwide and results in an economic and social burden that is both substantial and increasing. The purpose of the study was to explore the alteration of serum iron in patients with COPD. This cross-sectional study was carried out in the Department of Biochemistry, Mymensingh Medical College, Bangladesh from January 2021 to December 2021. Data was collected from Medicine Department of Mymensingh Medical College Hospital, Bangladesh. A total number of 120 subjects participated in this study. Out of them, 60 apparently normal healthy individuals were selected as Group I and another 60 diagnosed COPD patients were selected as Group II. Serum iron was measured by CAB method. Statistical package for social science (SPSS), version 21.0 was used for results calculation and analysis. Data were expressed in mean ±SD and statistical significance was done by Student's unpaired 't' test. The mean results of serum iron were 97.60±5.50 μg/dl in Group I and 49.80±5.92 μg/dl in Group II (p<0.001). This study found the relation between COPD and alteration of serum iron was statistically significant. So, by this study we recommended that routine evaluation of serum iron is important for prevention of exacerbations, reduction of morbidity and mortality in patients with COPD.