Sn–Sb–Co alloy films prepared via co-electroplating and post-electrodissolution treatment were studied as anode materials for lithium-ion batteries. The alloy was composed of pure Sn, Sn–Sb, and Sn–Co alloy phases. During post-electrodissolution, the easy dissolution of Sn phase resulted in an increase in Sb and Co contents. Electrochemical measurements showed improved initial capacity and capacity retention with increasing electrodissolution treatment time. For the sample subjected to 10 min of electrodissolution treatment, the capacity remained at 580 mAh g−1 at the 50th cycle. Post-electrodissolution was proven to be an effective method to improve the electrochemical performance of ternary Sn-based alloys.