Background:The supraclavicular brachial plexus block is a widely used technique for upper limb anesthesia due to its rapid onset and reliable coverage. This study aims to assess the incidence of pneumothorax following supraclavicular brachial plexus block.The aim of the study was to determine the incidence of pneumothorax following supraclavicular brachial plexus block.Methodology:This prospective observational study was conducted from January 2022 to December 2024 at Holy Family Red Crescent Medical College and Kalatia Central Hospital Pvt. Ltd.,Keranigonj, Dhaka, Bangladesh in the Department of Anesthesia, Analgesia & Intensive Care Unit. 200 patients undergoing supraclavicular brachial plexus block were enrolled. Blocks were done via ultrasound or landmark technique; needle angle and attempts were recorded. Patients were monitored for pneumothorax, confirmed by chest X-ray if suspected. Incidence and risk factors were analyzed descriptively.Results:The study included 200 patients (mean age 38.2 ± 19.1 years), with 55% males and an average BMI of 23.5 ± 3.8 kg/m2. Most were ASA Grade I (63.5%), and 90% received ultrasound-guided blocks. Pneumothorax occurred in 4 cases (2.0%), with a higher incidence in the landmark group (15%) compared to the ultrasound group (0.6%). Among pneumothorax cases, 50% had preexisting pulmonary conditions, 25% were obese, and 75% had a needle angle ≥45°, suggesting these as contributing risk factors. Conclusion:Ultrasound-guided supraclavicular brachial plexus block is associated with a lower risk of pneumothorax, highlighting the importance of careful technique and patient risk assessment.