The impact of ESG performance on corporate financial outcomes was examined using panel data from A-share listed companies in China spanning 2014-2024, with 2020 excluded due to exceptional circumstances. A mediation model was employed to explore the underlying mechanisms. The results indicated that strong ESG performance positively affected financial performance, with financing constraints and agency costs acting as partial mediators. Additionally, the effect of ESG performance was found to be more pronounced among low-pollution firms and small- and medium-sized enterprises. These findings provided important insights for strengthening ESG integration and advancing corporate sustainability.