Abstract: Ultrafine nano-scale Cu₂Sb alloy confined in a three-dimensional porous carbon was synthesized using NaCl template-assisted vacuum freeze-drying followed by high-temperature sintering and was evaluated as an anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). The alloy exerts excellent cycling durability (the capacity can be maintained at 328.3 mA·h·g⁻¹ after 100 cycles for SIBs and 260 mA·h·g⁻¹ for PIBs) and rate capability (199 mA·h·g⁻¹ at 5 A·g⁻¹ for SIBs and 148 mA·h·g⁻¹ at 5 A·g⁻¹ for PIBs) because of the smooth electron transport path, fast Na/K ion diffusion rate, and restricted volume changes from the synergistic effect of three-dimensional porous carbon networks and the ultrafine bimetallic nanoalloy. This study provides an ingenious design route and a simple preparation method toward exploring a high-property electrode for K-ion and Na-ion batteries, and it also introduces broad application prospects for other electrochemical applications.