Almost 30% of the global population is obese and overweight. In Pakistan, the latest research reveals that 28% of peoples are overweight and 16% obese. However, scarce data is available to report a relationship between obesity and pulmonary health in workers. For this reason, the current study aimed to study dynamics of pulmonary function parameters based on body mass index (BMI) categories, through a spirometer device, among wet-blue leather tannery workers. A total of 116 male tannery workers was selected as a studied population. Workers excluded who had age < 20 years, ever-smokers; respiratory disorders, cardiac illness, diabetes, and hypertension. The study was conducted between September to December 2019. Age, height, weight, and BMI were noted. The following BMI categories were used: normal-weight (18.5-24.9), overweight (25.0-29.9), and obese (≥ 30.0). The Pearson correlation test was run to determine was any linear correlation between pulmonary function parameters and BMI categories. Age, weight and BMI showed statistical differences in all BMI categories except height (P= 0.058). In obese and overweight workers, lower mean values of the pulmonary function parameters were observed compared to normal weight workers, respectively. A significant a significant linear correlation between FEV1 %, FVC % and BMI categories except for FEV1/FVC. It was concluded that obese and overweight workers might have reduced pulmonary function parameters. Future studies among tannery workers are highly recommended to find a correlation between BMI categories and pulmonary function with dust exposure. Keywords: Body mass index, Lung, Obesity, Overweight, Pakistan