[en] Metallic actuators have received a wide range of attention in the past two decades because of their larger strains than piezoelectric ceramics and higher strength relative to conducting polymers. However, the metallic actuators composed of noble metals are limited to the high material cost for further development and practical applications. Here, nanoporous CuMnNi (np-CMN) alloys are fabricated from a ternary Mn${}_{70}$Cu${}_{20}$Ni${}_{10}$ precursor through an electrochemical dealloying method, and their microstructures/compositions are further regulated through different electrochemical processes (multi-step and two-step). The np-CMN alloys show good electrochemical actuation properties in 1 m NaOH solution, and the sample obtained from two-step dealloying exhibits much better actuation performance than that from multi-step dealloying. The maximum strain amplitude of np-CMN could reach up to 0.46%, which is comparable to or even better than that of noble metal-based actuators. Our work indicates that the low-cost np-CMN alloy could be a competitive material among electrochemical metallic actuators. (© 2022 Wiley‐VCH GmbH)