ABSTRACT In the current investigation we formulated and evaluates matrix tablet using modified gum of Pistacia lantiscus gum (PLMG) as natural matrix forming agent used in various successively increasing concentration. The pre-compression study of the powder blends of drug, PLMG and other excipients were done by calculating bulk density, tapped density, angle of repose and carr’s index (% compressibility) and hausner’s ratio. The tablets using PLMG as matrix forming agent were prepared by direct compression method and prepared tablets were evaluated for thickness, hardness, weight uniformity, friability and content uniformity and were found according to the official guidelines by pharmacopoeia. The swelling behavior of prepared matrix tablets was studied using for 12 hours at 37 ±0.2 0C, it was fond that the drug to modified gum ratio of 1:2 was found to be optimum swelling with the sustained release of model drug up to 97.12 in matrix tablet formulation. The results revealed, that modified fraction of Pistacia lantiscus gum can be used as a drug release modifier to delay as the rate of drug release of which depended on the amount of gum composition, as the concentration of gum was increased there was sustain the drug release. Keywords: Pistacia lantiscus, tablet, modified gum, diclofenac potassium, hausner’s ratio.