The objective of this study was designed to elucidate the importance of adding pluronics to PCL microparticles for the delivery of proteins. The influences of the type and the amount of pluronic on the surface morphology and release properties of protein-loaded PCL microparticles were evaluated. Microparticles were prepared by the w/o/o/o solvent evaporation technique with an ultrasonicator. All of the microparticles prepared were spherical in shape, with a rough surface due to crystallization of PCL in the microparticles. The pluronics efficiently prevented microparticles from aggregation, and the size of microparticles prepared was significantly reduced. The significant increase in the encapsulation efficiency and decrease in the burst release of protein from PCL microparticles were achieved by using pluronic F127. Incorporation of pluronic F127 increased the hydrophilicity of the matrix, which further retained protein in blended microparticles. Both pluronics PE10100 and L61 significantly reduced the crystallinity of PCL microparticles. Nevertheless, this result did not further influence the release property of BSA from these microparticles.