Climate change mitigation requires simultaneous reduction of carbon emissions and air pollution. This study examines the synergy between pollution reduction and carbon reduction, identifying key variables and strategies to achieve this goal. Using a Geographical Detector model and a Coupling Degree of Coordination model, 108 cities in the Yangtze River Economic Belt (YREB) are investigated. Results show that while controlling PM2.5 has been more successful than managing carbon emissions in the YREB, synergy between pollution reduction and carbon emissions increased by an average of 7.2% from 2006 to 2019. Spatial analysis reveals higher synergy in upstream areas, indicating significant spatial diversity. The impact of pollution and emission reduction synergies is influenced by societal and environmental variables, including industry structure, technological innovation, energy structure, human capital quality, and economic basis. Synergy is amplified when natural limits align with high-quality development drivers such as technical innovation and the digital economy. Recommendations include enhancing city-to-city contact, improving energy and industrial structures, and fostering technological innovation to address regional variations in synergy levels.