Objective: The objective of this study was to formulate and evaluate the drug release studies using Poly (ε-caprolactone) (PCL)/and Poly (R)-3-hydroxy butyric acid (PHB) blend microspheres for controlled release of Tamoxifen, an anticancer drug.Methods: Poly (ε-caprolactone), Poly ((R)-3-Hydroxybutyric acid) blend microspheres were prepared through a modified Water/Oil/Water (W/O/W) double emulsion-solvent diffusion method using Dichloromethane as solvent. Tamoxifen (TAM), an anti Cancer drug, was used for encapsulation within PCL/PHB blend microspheres. Morphology, size, encapsulation efficiency and drug release from these microspheres were evaluated by different characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimetry(DSC), Scanning electron microscopy(SEM), X-ray diffraction studies(X-RD) and dissolution test studies respectively.Results: Drug loaded microspheres were analyzed by FT-IR, which indicates the interaction between drug and polymers. DSC thermograms on drug-loaded microspheres confirmed the polymorphism of Tamoxifen and indicated a molecular level dispersion of drug in the microspheres. SEM confirmed the spherical nature and smooth surface of the microspheres produced. X-RD study was performed to understand the crystalline nature of the drug after encapsulation into the microspheres and confirmed the complete dispersion of the drug in the polymer matrix. In-vitro release studies conducted in different pH which indicated a dependence of release rate on the amount of drug loading and the amount of PCL/PHB, but slow release rates were extended up to 12 h. Kinetic analysis of dissolution data showed a good fit in Peppas equation confirming diffusion controlled drug release.Conclusions: The research findings obtained from the studies were found to be satisfactory. It can be concluded that biodegradable polymer blend (PCL/PHB) microspheres can be effectively used for preparation of controlled release matrices. Â