Aqueous alkaline Zn‐based batteries (AAZBs) possess great promise for large‐scale applications thanks to their higher discharging plateau and unique reaction mechanism. However, the capacity and rate capability of Ni‐based cathodes are still unsatisfactory due to their insufficient OH− adsorption and diffusion ability. Herein, heterostructured Ni3S2/Ni(OH)2 nanosheets with outstanding electrochemical performance are synthesized via a facile chemical etching strategy. The heterostructured Ni3S2/Ni(OH)2 nanosheet cathode shows significantly increased capacity and rate capability due to its boosted OH− adsorption and diffusion ability compared to Ni3S2. Consequently, the assembled Zn//Ni3S2/Ni(OH)2 cell can deliver an ultrahigh capacity of 2.26 mAh cm−2, an excellent rate performance (0.91 mAh cm−2 at 100 mA cm−2) and a satisfying cycling stability (1.01 mAh cm−2 at 20 mA cm−2 after 500 cycles). Moreover, a prominent energy density of 3.86 mWh cm−2 is obtained, which exceeds the majority of recently reported AAZBs. This work is expected to provide a new modification direction for developing high‐performance nickel sulfide cathode for AAZBs.