Anti-mPEG/anti-human epidermal growth factor receptor 2 (HER2) bispecific antibodies (BsAbs) non-covalently bound to a docetaxel (DTX)-loaded mPEGylated lecithin-stabilized micellar drug delivery system (LsbMDDs) were endowed with active targetability to improve the chemotherapeutic efficacy of DTX. DTX-loaded mPEGylated LsbMDDs formulations were prepared using lecithin/DSPE-PEG(2K or 5K) nanosuspensions to hydrate the thin film, and then they were subjected to ultrasonication. Two BsAbs (anti-mPEG/anti-DNS or anti-HER2) were simply mixed with the LsbMDDs to form BsAbs-LsbMDDs formulations, respectively, referred as the DNS-LsbMDDs and HER2-LsbMDDs. Results demonstrated that the physical characteristics of the BsAbs-LsbMDDs were similar to those of the plain LsbMDDs but more slowly released DTX than that from the LsbMDDs. Results also showed that the HER2-LsbMDDs suppressed the growth of HER2-expressing MCF-7/HER2 tumors, increasing the amount taken up via an endocytosis pathway leading to high drug accumulation and longer retention in the tumor. In conclusion, the BsAbs-LsbMDDs preserved the physical properties of the LsbMDDs and actively targeted tumors with a drug cargo to enhance drug accumulation in tumors leading to greater antitumor activity against antigen-positive tumors.