The objective of the present investigation is to synthesize calcium starch, a new starch based polymer and to evaluate its application in controlled release (CR) and in the design of diclofenac controlled release tablets. Calcium starch polymer was synthesized by gelatinization of starch in the presence of sodium hydroxide and cross linking by treatment with calcium chloride. Matrix tablets each containing 100 mg of diclofenac sodium were formulated employing calcium starch polymer in different proportions of drug and polymer and the tablets were evaluated. Diclofenac release from the formulated tablets was slow and spread over 24 h and depended on percent polymer in the tablet. Release was diffusion controlled and followed zero order kinetics. Non – Fickian diffusion was the drug release mechanism from the formulated tablets. Diclofenac release from matrix tablets F3 formulated employing 15 % calcium starch was similar to that from Reactin SR tablets, a commercial sustained release formulation of diclofenac. Calcium starch polymer was found suitable for the design of oral controlled release tablets of diclofenac.