Size of the microparticle and integrity of the released protein are two crucial factors which dictate the success of any protein or vaccine delivery system. The primary objective was to optimize bovine serum albumin ( BSA) loaded polycaprolactone/ maltodextrin ( PCL/ MD) microparticles in terms of its size and the hydrodynamic diameter of the released protein. The effect of size determining formulation process variables ( SDFPV) of microparticles on the hydrodynamic diameter of protein antigen was determined. The SDFPV were optimized by a compromise between the microparticle size and the relative hydrodynamic stability of protein released from it. Percentage of secondary structure of the protein released from the optimized formulation as determined by circular dichroism spectra along with SELCON software was also similar to that of native BSA suggesting the potential of PCL/ MD microparticles for protein or vaccine delivery.