Herein we report the synthesis of polymer coated quantum dots (QDs)-carbon nanotube composite material with high biocompatibility and low cellular toxicity. The synthesized multi-walled carbon nanotube (MWCNT)-QD-(-poly(glycidyl methacrylate)) (pGMA) hybrids were characterized using X-ray photoelectron spectroscopy, laser scanning confocal microscopy, transmission electron microscopy and scanning electron microscopy. The results showed that quantum dots were well-distributed on nanotube surfaces in high density. The toxicological assessments of QDs and MWCNT-QD-polymer hybrids in human mammary carcinoma cells and their fluorescence imaging in living cell system were carried out. MWCNT-QD-polymer hybrids possess intense red fluorescence signal under confocal microscopy and good fluorescence stability over 6-h exposure in living cell system. The toxicity comparison of QDs and MWCNT-QD-polymer hybrids has shown that the existence of PGMA thin coating on MWCNT-QD hybrid surface decreased the cellular toxicity and increased biocompatibility.