The administration of poorly bioavailable drug through parenteral route is regarded the most efficient for drug delivery. Parenteral delivery provides rapid onset even for the drug with narrow therapeutic window, but to maintain the systemic drug level repeated installation are required which cause the patient discomfort. This can be overcome by designing the drug into a system, which control the drug release even through parenteral delivery, which improve patient compliance as well as pharmacoeconomic. One of the such system is injectable in-situ gelling system This biodegradable injectable in-situ gelling drug delivery system offer attractive opportunities for protein, anti cancer or NSAIDs drug delivery and could possibly extend patent life of these drugs. This article explores the injectable in-situ gelling system for prolonged release parenteral drug delivery system and their strategies of preparation, their potential benefits/drawbacks mechanism of work and in-vitro testing methods.