Polyglycerol (PG) functionalization on the surface of nanoparticle is one of the most effective methods to well disperse the particle in a physiological environment. The functionality also provides the nanoparticle with scaffold for further derivatization to add more functions. In this chapter, we will describe PG functionalization of nanoparticles including detonation nanodiamond (dND), superparamagnetic iron oxide nanoparticle (SPION) and fluorescence nanodiamond (fND), and their further derivatization for biomedical imaging agents in magnetic resonance and fluorescence imaging.