Background: Rheumatoid arthritis (RA) is a chronic inflammatory disease primarily affecting joints but often associated with systemic complications, including pulmonary involvement. Pulmonary function tests (PFTs) provide valuable insights into respiratory involvement in RA, but their correlation with disease activity remains underexplored. Objective: To evaluate the relationship between PFT parameters and disease activity in RA patients and compare findings with healthy controls. Methodology: A case-control study was conducted over three months, involving 50 RA patients (cases) and 50 age- and sex-matched healthy individuals (controls). Cases were assessed using the Disease Activity Score-28 (DAS28) and underwent spirometry to measure Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), FEV1/FVC ratio, Peak Expiratory Flow Rate (PEFR), and Forced Expiratory Flow (FEF 25-75%). Data were analyzed using statistical software, with a p-value <0.05 considered significant. Results: RA cases exhibited significantly higher abnormal PFT parameters compared to controls, with 44% showing restrictive lung function abnormalities. Abnormal FVC% predicted was observed in 46% of cases versus 2% of controls (OR=26.4, p<0.00001). Abnormal PEFR% predicted and FEF 25-75% were also more prevalent in cases (52% and 78%, respectively) compared to controls (26% and 58%). A strong association was observed between higher disease activity (DAS28 >7) and abnormal pulmonary function. Conclusion: Pulmonary involvement is a significant extra-articular manifestation of RA, with restrictive abnormalities being most common. A strong correlation exists between disease activity, inflammatory markers, and impaired lung function. Regular monitoring of pulmonary function in RA patients is essential for early detection and management of respiratory complications.