Abstract: Provided herein are dendrimer-targeting agent conjugates comprising a dendrimer, the dendrimer comprising a core unit and lysine or lysine analogue building units, a HER2 targeting agent which is a peptidic moiety having a molecular weight of up to about 80 kDa and comprising an antigen-binding site, which is covalently linked by a spacer group, and a therapeutic agent which is covalently linked to a surface building unit of the dendrimer. Also provided herein are compositions comprising the conjugates, and therapeutic methods using the conjugates, particularly for treating cancer.