This study investigates the particle size distribution of Labetaol HCl using the Malvern Mastersizer 3000 in wet analysis mode. The research focuses on method validation through precision, intermediate precision, robustness, accuracy, and comparison with microscope methods and different versions of the Malvern instrument. Results demonstrate high precision with % RSD values within acceptable limits for all particle sizes tested. The robustness study confirms method reliability under varied conditions. Comparative analysis between Malvern 2000 and Malvern 3000 instruments shows consistent measurements meeting specified criteria. This study validates the Malvern Mastersizer 3000 for precise particle size analysis of Labetalol HCl, essential for pharmaceutical quality control and compliance.