Additive interface materials for improved ionic polymer metal composite (IPMC) actuator performance are being investigated. In this study, three-dimensional carbon nanostructure/copper nanowire (3DC Cu-NW) with a novel structure was synthesized via low-pressure chemical vapor deposition. An IPMC actuator with a 3DC Cu-NW interface layer was fabricated, which exhibited improved actuation performance, long-term stability, and electrochemical properties. The proposed 3DC consists of carbon nanotubes (CNTs) and graphene, grown using an Fe catalyst and CH gas, respectively. We optimized the growth conditions (Fe catalyst: 12.5 mg/L, CH : 20 sccm) to achieve a 3DC with an appropriate thickness and a large specific surface area. The 3DC Cu-NW benefited from a Cu oxidation prevention property and a large specific surface area. The electrochemical properties and actuation performance of the IPMC actuator improved with an increased 3DC Cu-NW concentration. An IPMC actuator with a 0.6 wt% 3DC Cu-NW interface layer exhibited 1.3- and 5.6-fold electrochemical property and actuation performance improvement, respectively, over an IPMC actuator with no 3DC Cu-NW interface layer. These results show that the proposed 3DC Cu-NW has potential as an IPMC actuator interface material, and that 3DC Cu-NW synthesis and application technology can be applied to future research on sensor, actuator, and flexible devices.