Background: Diabetes mellitus is a metabolic disorder with multifactorial etiology. Type 2 diabetes (T2DM) occurs due to inadequate insulin secretion and resistance to insulin action. In India, the burden of diabetes expected to rise to over 134 million by 2045 in India. Pulmonary complications of diabetes mellitus have been poorly categorized. The duration of diabetes and glycaemic status has shown marked emphasis on functions of the lungs. The aim of our study was to determine the effect of glycaemic status and duration of diabetes on pulmonary function in spirometry among type 2 diabetes mellitus patients. Materials and Methods: This is a cross-sectional study involving 140 type 2 diabetes mellitus patients. The study participants were subjected to cosmed computerized spirometer to assess pulmonary function tests. The data obtained was analysed using unpaired student’t’ test and to find the association, Pearson’s correlation test was used.The pulmonary function tests were compared with duration of diabetes by ANOVA test. The p value < 0.05 was taken as level of statistical significance. Results: The findings of our study revealed that there was a statistically significant reduction in mean values of FVC, FEV1, PEF, MIP, MEP and raised FEV1% among type 2 diabetic patients with poor glycaemic control and long duration of diabetes in comparison to subjects with good glycaemic control and relatively short duration of diabetes. Also, there was a statistically significant negative linear correlation between FVC, FEV1, PEF, MIP, and glycaemic status (p<0.05). The study findings suggest that there is a restrictive pattern of pulmonary impairment among the type 2 diabetes mellitus patients. Conclusion: The development of pulmonary impairment among the type 2 diabetes mellitus patients is strongly associated with poor glycaemic control and long duration of diabetes. Therefore, periodic assessment of lung function by spirometry tests and intensive glycaemic control can avert or delay the hyperglycaemia induced progressive lung damage in diabetic individuals.