A novel liposome/hydrogel soft nanocomposite was explored as a controlled drug delivery system. A P2VP-PAA-PnBMA biocompatible, pH-responsive triblock terpolymer was used as an injectable gelator, entrapping PC/Chol liposomes loaded with calcein as hydrophilic model drug. The composite hydrogel was formed in vitro through a pH-induced sol-gel transition by dialysis against buffer under physiological conditions and at polymer concentration as low as 1 wt %. Excellent control of the calcein release was achieved just by adjusting the gelator concentration; that is, from 1 to 1.5 wt %, the drug release period was significantly prolonged from 14 to 32 days.