Abstarct: Flotation, as one of the most important mineral processing techniques, plays a fundamental role in the recovery of valuable minerals, particularly lead and zinc, from various ore deposits. However, challenges such as reduced recovery and process instability especially in the treatment of fine particles have limited the efficiency of this method. In this context, the application of stable micro–nano bubbles has recently attracted considerable attention as an emerging approach and has been proposed as an effective strategy for improving flotation performance and enhancing process efficiency. Accordingly, the objective of this study is to investigate the effect of stable micro–nano bubbles on the flotation performance of the Shahrestanak lead–zinc ore (Qom, Iran). The experiments were designed and conducted under varying operational and chemical conditions, both in the presence and absence of micro–nano bubbles. XRF analysis of the feed sample revealed that the ore is predominantly composed of SiO₂ and CaO, while the mextallic phases ZnO and PbO accounted for 13.7% and 3.8%, respectively. The relatively high contents of Fe₂O₃ and Al₂O₃ indicate the presence of iron-bearing and aluminosilicate phases, which may limit the accessibility of mextals to bubbles. Using a hydrodynamic cavitation-baxsed micro–nano bubble generator, bubbles in the nanometer range (80–105 nm) and micrometer range (0.7–1.15 μm) were produced and introduced into the flotation system. The effects of operational and chemical parameters, including pulp pH, collector concentration (SIPX and PAX), depressants (ZnSO₄ and NaCN), activator (CuSO₄), frother (MIBC), and flotation kinetics, were investigated separately for the lead and zinc circuits. Results showed that the presence of micro–nano bubbles enhanced mextal recovery, improved concentrate grade, and accelerated flotation kinetics under all experimental conditions. Specifically, lead and zinc recoveries increased by 4–6% and 3–5%, respectively, compared to conventional flotation. The optimal flotation conditions for the lead circuit were pH 8, 200 g/t SIPX, 300 g/t zinc sulfate, 100 g/t sodium cyanide, and 80 g/t MIBC, resulting in a lead recovery of approximately 69.89%. For the zinc circuit, pH 9, 300 g/t copper sulfate, 100 g/t PAX, and 80 g/t MIBC provided the highest zinc recovery and grade. Kinetic analysis indicated that micro–nano bubbles improved the transfer rate of mextallic particles to the froth phase and enhanced the flotation kinetic constant. Overall, the findings demonstrate that the optimized combination of chemical and operational parameters, in conjunction with micro–nano bubble technology, can significantly enhance the flotation performance of lead–zinc ores and serve as a basis for the design and optimization of industrial-scale flotation circuits.