The use of human growth hormone (hGH) as a therapeutic protein has been limited by its instability in biological fluids and short biological half-life in vivo. In this study, glycol chitosan (GC) bearing beta-cyclodextrin (GC-betaCD) as the carrier of hGH was synthesized by the covalent attachment of a carboxymethyl derivative of betaCD to the GC backbone via amide bond formation. The GC-betaCD conjugate could form self-assembled nanoparticles (340 nm in mean diameter) in an aqueous solution, resulting from hydrogen bonding among betaCDs at the backbone of the conjugate. hGH was effectively encapsulated into the nanoparticles because of hydrophobic interactions between the hydrophobic cavity of betaCD and alkyl or aromatic groups of amino acids in hGH. From the in vitro release experiments, it was found that the nanoparticles released hGH in a sustained manner for 9 days. Overall, the GC-betaCD conjugate might be a promising carrier for sustained delivery of hGH.