Abstract: China has entered a new stage with the coordinated governance of pollution control and carbon emissions reduction. In the Yangtze River Delta Region, it is necessary to synergistically promote pollution reduction, carbon reduction, and high-quality economic development to achieve carbon peak and carbon neutrality goals, and regional high-quality integrated development. In this context, the synergistic effects of environmental policies that can promote carbon reduction, pollution reduction, green expansion, and growth are of great significance for the overall green transformation of economic and social development. A panel comprising 41 prefectural-level cities in the Yangtze River Delta Region was selected to conduct an empirical study from 2006 to 2020. With air pollutant (including SO₂, NO_x, PM and VOCs) emissions equivalent, carbon emissions and the level of high-quality economic development as the explanatory variables, and pollution reduction and carbon reduction policy strength as the core explanatory variables, the synergistic effects of policies related to air pollution, carbon emissions, and high-quality economic development were tested by constructing a fixed effects model, and the mechanism involved was assessed by constructing an intermediary effects model. (1) The pollution reduction and carbon reduction policies had three significant synergistic effects. On average, each 1% increase in the policy strength decreased air pollution by 0.470% and carbon emissions by 0.292%, and increased regional high-quality economic development level by 0.040%. (2) The effects of the pollution reduction and carbon reduction policies were heterogeneous among regions. Only the core city group achieved the three synergistic effects, whereas only pollution reduction was realized in the central city group, and the policies had no effect in the peripheral city group. (3) Two energy consumption and green technology innovation paths were identified for achieving the three synergistic effects of the pollution reduction and carbon reduction policies. Differentiated policies need to be adapted to regional conditions to enhance the synergistic effects of policies, in order to comprehensively realize air pollution and carbon reduction, and high-quality economic development in the Yangtze River Delta Region.