The purpose of present study was to develop controlled release microspheres for oral delivery of Aceclofenac. The microspheres were prepared by Oil-in-Oil (O/O) emulsion solvent evaporation technique using polymer blend of HPMCP and ethyl cellulose. D-Optimal response surface design was used to statistically optimize the effect of drug polymer ratio and stirrer speed on selected variables of microspheres. The results showed that size of microspheres were from 81.08 to 192.5μ depending on the experimental condition. The encapsulation efficiency was achieved as high as 89.71%. The SEM study indicated that the microspheres from the optimized batch were of rough surface. The in-vitro release study showed that the microspheres gave biphasic release where microspheres showed negligible release in 0.1N HCl and gave extend release up to 24h in phosphate buffer pH 6.8. The accelerate stability study indicated that the formulation was stable.