Background: In this study, we developed pegylated (poly(D,L-lactide-co-glycolide) (PLGA-PEG) nanoparticles for loading docetaxel and improving active target in cancer cells because it’s advantages over other nanocarriers such as excellent biocompatibility, biodegradability and mechanical strength and these nanoparticles were conjugated with molecules of a novel anti-HER2 single chain fragment (scFv) by a simple carbodiimide modified method. ScFvs have potential advantages over whole antibodies such as more rapid tumor penetration and clearance. In addition, to investigate cellular uptake of targeted nanocarriers, many studies had performed by linking with fluorescent factors but in this study 6-histidine-tag fused with novel anti-HER2 scFv antibodies can be used to purify protein and study binding activity and cellular uptake of targeting nanoparticles that it was not changed their characterization in vitro. Furthermore, cytotocixity of these nanoparticles was also investigated in BT474 (HER2 overexpress) and MDA-MB-231 (HER2 underexpress) cells. Results: Docetaxel loaded nanoparticles (Doc-NPs) with a mean size of 105 nm and zeta potential of -25 mV were prepared by nanoprecipitation method. Conjugation of a novel single chain fragment of antibody against epidermal growth factor receptor 2 to Doc-NPs by covalent coupling via cross-linker EDC and NHS resulted in an increase of mean size and zeta potential of targeted nanoparticles (scFv-Doc-NPs) with 135 nm and -32 mV respectively. The scFv- Doc-NPs bound specifically to BT474 cells but no MDA-MB-231 cells was investigated by flow cytometry. Especially, confocal fluorescence scanning microscopy revealed internalization of the scFv-Doc-NPs by the targeted cancer cells through anti-Histag antibodies with Alexa Fluori£¨ 546. Moreover, the scFv-Doc-NPs showed stronger cytotoxicity on BT474 cells than MDA-MB-231 cells with IC50 values of 0.234 and 0.535 μM, respectively. Conclusion: Here we report anti-HER2 scFv labeled and docetaxel loaded PLGA-PEG nanoparticles in order to broaden the applications of this new targeted drug delivery system in the therapy of HER2 overexpressed cancers. Also, this drug delivery system represents a promising approach to improve the efficacy of nanoparticles in active targeting for HER2-overexpressed cancer therapy.