The present study was designed to investigate the effect of plasticizer i.e., triethyl citrate (TEC) on the in vitro drug release kinetics of Rabeprazole sodium from sustained-release pellets. Ammonio-methacrylate copolymer type B (Eudragit RS 100) was used as the release-retarding polymer. The plasticizer was used in different concentrations i.e. 0%, 5%, 10% 15%, and 20% (w/w) of Eudragit 100. Pellets were prepared by powder layering technology and coated with Eudragit RS 100 D using pan coating. Dissolution study was performed by using USP apparatus 2 (paddle type). When dissolution was performed on the pure drug, about 6.28% and 92% drug was dissolved in 2 h in 0.1 N HCl and in 30 min in buffer (pH 7.4), respectively. On comparing all formulations the release of drug in acidic dissolution medium was very negligible except the F1 formulation. It could have resulted due to the nonincorporation of triethyl citrate in Eudragit coating solution. It was observed that in buffer only 62% drug was released after 5 h from enteric coated pellets (F5) containing 20%TEC, thus indicating that Eudragit RS 100 significantly retarded the drug release rate and that drug release was varied according to the amount of plasticizer used. The amount of triethyl citrate in coating formulation significantly affected the drug release profile of the drug.