Patient’s compliance can be enhanced by using extended release drug delivery systems which allow decreasing the number of daily doses, and helping to maintain uniform drug levels and increase the safety margin for high-potency drugs. Hydroxypropyl methylcellulose (HPMC) is the most commonly used hydrophilic polymer for the preparation of oral controlled drug delivery systems. This research was conducted with the aim of  developing matrix based oral controlled release tablets for the drug diclofenac sodium using different viscosity grades of HPMC (K15M) and to compare the  drug release characteristics with those of a commercial product, Voltaren® SR 100. Similarity factor (f2), values in between test formulation and marketed preparation was calculated to choose the best formulation. The release kinetics from various matrices was also studied. Increasing in polymer content reduced the rate of drug release. At the same polymer content in the matrix, the drug release was most sustained with tablets prepared using HPMC (K15M). Out of all the formulations studies, matrix tablets containing 40% of HPMC (K15M) showed comparable dissolution profile to that of the marketed preparation as indicated by a similarity factor value of (f2) 88.30%. The release of drug from marketed preparation and matrix with HPMC (K15M) 40% was found to be a diffusion drug mechanism as per Higuchi equation.