The present study was undertaken to investigate the release retardant potential of Borassus flabellifer mucilage in tablet formulations. In the present study six batches of diclofenac sodium matrix tablets were prepared by wet granulation method with different concentrations of BFM (2.5, 5, 7.5,10 and 12.5%w/w) and compared with guar gum as standard release retardant polymer. The tablets had uniform physical appearance, average weight, drug content, and adequate hardness. The results of in vitro release revealed that as the proportion of mucilage in the matrix was increased there was a corresponding decrease in the release of drug. Among the formulations studied formulation F5 containing BFM in the concentration of 12.5% showed sustained and required dissolution profile of drug for 12hrs with cumulative percent release of 98%. Further, the matrix tablets were found to release the drug by diffusion coupled with erosion mechanism. The swelling studies revealed that, as the proportion of mucilage in tablets was increased, there was a corresponding increase in percent swelling of tablets. The SEM photomicrographs showed both pores and gelling structures were present on the surface of tablets indicates the combination of diffusion and erosion mechanism in the release of diclofenac. No chemical interaction between drug, mucilage and mixture of mucilage/drug was seen as confirmed by DSC and IR studies. Optimized formulation (F5) showed no change in physical appearance, drug content, or in dissolution pattern after storage at 40±2°C and 75±5% RH for 3 months.