Novel injectable biodegradable glycol chitosan hydrogels were developed based on thiolated glycol chitosan (GC-SH) and water soluble oligo(acryloyl carbonate)-b- poly(ethylene glycol)-b-oligo(acryloyl carbonate) (OAC-PEG-OAC) triblock copolymers via Michael-type addition reaction. The rheology measurements showed that robust hydrogels were formed rapidly upon mixing aqueous solutions of GC-SH and OAC-PEG-OAC at remarkably low total polymer concentrations of 1.5–4.5 wt % under physiological conditions. The gelation times (varying from 10 s to 17 min) and storage moduli (100 to 4300 Pa) of hydrogels could be controlled by degrees of substitution (DS) of GC-SH, solution pH, and polymer concentration. These glycol chitosan hydrogels had microporous structures, low swelling and slow hydrolytic degradation (stable for over 6 months) under physiological conditions. Notably, these hydrogels were prone to enzymatic degradation with lysozyme. The multiple acryloyl functional groups of OAC-PEG-OAC allowed facile conjugation with thiol-containing biomolecules prior to gelation endowing hydrogels with specific bioactivity. The preliminary cell culture studies revealed that these glycol chitosan hydrogels were cell non-adhesive while Gly-Arg-Gly-Asp-Cys (GRGDC) peptide modified hydrogels could well support adhesion and growth of both MG63 osteoblast and L929 fibroblast cells. These rapidly in situ forming enzymatically biodegradable hybrid hydrogels have great potentials in the development of injectable cell-specific bioactive extracellular matrices for tissue engineering. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.