Objective: The present study was aimed to investigate the controlled release of a water soluble drug, metoprolol, from α-lactalbumin microparticles. Methods: The microparticles were prepared by steric-stabilization process using lactic acid as the stabilizing agent. Metoprolol succinate loaded α-lactalbumin particles were characterized using particle analyzer, Fourier transform infra red spectroscopy, X-ray diffraction and scanning electron microscopy. Results: It was found that the size of the particles was in the range of 1-2 m and had encapsulation efficiency of 70 - 80%. The in vitro release studies of the encapsulated drug were performed under two simulated conditions of body fluids (SGF and SIF). The results indicated controlled release of about 70% of the encapsulated drug over a period of 24 hours, compared to the release of more than 90% of the drug (within two hours) from a physical mixture of α-lactalbumin and metoprolol succinate. Conclusions: The results thus offer hope for the design of drug delivery system using lactic acid-stabilized α-lactalbumin microparticles for the controlled release of metoprolol succinate. Using lactic acid to prepare α-lactalbumin microparticles provides improved biocompatibility in comparison to chemically cross-linked microparticles.