The study aims at formulation and characterization of three months parenteral risperidone loaded polymeric microspheres (p-RLPMs) as a sustained delivery system and established their in vitro and in vivo assessments. The p-RLPMs formulations were prepared by solvent extraction and diffusion method. The optimized p-RLPMs (batch RPLGA-1) formulation demonstrated favorable different physicochemical properties such as mean particle size (104±5.34 μm), percent porosity (44.56±3.11%) and percent drug loading (38.42±2.67%). The physical state characterization, Fourier transformed infrared spectroscopy analysis showed no changes in the chemical structure of risperidone (RPD) in the batch RPLGA-1 formulation and differential scanning calorimetry study confirmed, pure RPD retained its crystallinity in the batch RPLGA-1 formulation. The SEM micrographs of the all p-RLPMs formulations revealed the irregular shapes and indentations. The GC/MS results showed that the residual organic solvent content in the batch RPLGA-1 formulation was below the limits. Pharmacokinetic parameters revealed that optimized RPLGA-1 formulation exhibited an initial burst followed by an excellent sustained release as compared to pure RPD as well as other formulations. Furthermore, in vivo studies of the batch, RPLGA-1 formulation showed an antipsychotic effect that was significantly prolonged over that of pure RPD solution for up to 72 h with fewer extrapyramidal side effects. Thus, results of this study prove the suitability of using poly(lactic-co-glycolic acid) copolymer to develop sustained release p-RLPMs formulations that can tailor in vivo behavior and enhance the pharmacological effectiveness of the RPD.