Applications of nanodiamonds (NDs) to bioimaging are restricted because of the nonspecific adsorption of biomolecules on the surface of NDs. Here, we show that hyperbranched polyglycerol-modified nanodiamond realizes both excellent dispersibility and marked suppression of nonspecific adsorption to proteins. Moreover, selective targeting to the proteins of interest, and the measurement of optically detected magnetic resonance from this nanodiamond on living cells are demonstrated.