A solid-electrolyte interphase (SEI) is highly desirable to restrain Zn dendrite growth and side reactions between a Zn anode and water in rechargeable aqueous zinc-ion batteries (RAZBs), but remains a challenge. Here, inspired by the bio-adhesion principle, a stable SEI of polydopamine is constructed successfully on a Zn anode via an in situ electrochemical polymerization process of a dopamine additive. This in situ polymeric SEI offers multifunctional features with abundant functional groups and outstanding hydrophilicity for regulating Zn nucleation to achieve dendrite-free Zn deposition, high Zn-ion conductivity for fast Zn2+ transport, and strong adhesion capability for blocking interfacial side reactions. Consequently, the Zn electrodes exhibited high reversibility with 99.5% coulombic efficiency and outstanding stability, even at ultrahigh current density and areal capacity (30 mA cm-2 and 30 mA h cm-2). Moreover, a prolonged lifespan can be attained for the Zn/V2O5 full cell in a lean electrolyte (9 μL mA h-1) and with a low capacity ratio of the negative electrode to the positive electrode (∼2). This work provides inspiration for the design of SEI layers in aqueous battery chemistry and promotes the practical application of RAZBs.