The objective of this research is to investigate the role of Sb addition on the microstructure and creep behaviors of the Sn–6.5Zn–0.3Cu solder alloy. Concerning microstructure examinations, the results exhibited that the Sb addition to the Sn–6.5Zn–0.3Cu alloy successfully produced uniform dispersion of γ-Cu5Zn8 and Sb2SnZn intermetallic compounds (IMCs) along with α-Zn and β-Sn matrix, resulting in the microstructure refinement. In addition, because Cu–Zn and Sb– Sn–Zn IMC particles formed, the adverse effects of the oxidation resistance of Zn were reduced. The results showed that the microstructure and creep behaviors of the Sn–6.5Zn–0.3Cu-based alloy improved with Sb addition. Specifically, the creep resistance of the Sn–6.5Zn–0.3Cu alloy was greatly improved by the addition of 3.0 Sb and 1.0 Sb, resulting in enhancements of around 460% and 170%, respectively, due to the solid solution and finely dispersed IMCs. Due to the solid solution’s strengthening and the various dispersed IMCs, the Sb-containing solder alloys also displayed prolonged creep lifetimes and the highest stress exponents. In view of results, the microalloying of Sb in Sn–6.5Zn–0.3Cu-based alloy has produced dependable, high-performance creep properties that satisfy the needs of the industrial applications.