The aim of the present work was formulation and evaluation of in situ gelling system of cytarabine. Cytarabine is an anti-cancer agent, which exhibits less oral absorption, less site targeted ability and show toxic effect (higher amount), when given in the form of conventional injectable solutions. To overcome this, an attempt has been made to formulate pH-triggered or ion exchange in situ gelling system of cytarabine to provide sustained release of drug based on polymeric carriers that undergo sol-to-gel transition upon change in pH. The cytarabine in situ gelling system formulated by using poly acrylic acid (Carbopol 934 NF) in combination with sodium alginate, which acted as viscosity enhancing agent. The developed formulation was stable, non-irritant and provided sustained release over 24-hour period and it is a viable alternative to conventional injectable.