Bispecific antibody - drug conjugates represent an innovative concept for cancer therapy, which integrates the merits of both antibody - drug conjugates and bispecific antibodies. In this study, a proof-of-concept biomimetic bispecific antibody based on an albumin binding domain fusing with camelid-derived nanobodies was devised to deliver anti-cancer drugs to replicate the two most distinctive features of ADCs: long-acting in vivo and tumor targeting, while reducing products heterogeneity and production cost. To validate this concept, an anti-EGFR nanobody and an anti-HER2 nanobody were used as model sequences to construct biomimetic bispecific antibodies. The biomimetic bispecific antibodies were efficiently expressed in Escherichia coli bacteria and produced at considerably low cost, and the model cytotoxic payload (mc-vc-PAB-MMAE) were site-specifically coupled to the fusion protein through a cysteine-maleimide based conjugation approach. These bispecific protein-MMAE conjugates were well characterized in vitro , and exhibited prolonged circulation times in healthy rats and superior anti-tumor efficacy in an A549 xenograft mice model. The works could provide a general strategy for design of biomimetic bispecific ADCs for cancer therapies.