The present invention relates to anti-HER2 binding molecules (e.g., antibodies and antigen binding fragments thereof), derived HER2-binding molecules (e.g., bispecific anti-HER2 antibodies), and antibody-drug conjugates (ADC) that bind the extracellular domain of the HER2 receptor. Also provided are pharmaceutical formulation comprising the disclosed compositions and method for the treating diseases associated with HER2-mediated signal transduction.