Abstract: Against the backdrop of advancing rural revitalization and the green transformation of economic and social development, whether agritourism integration can simultaneously improve the ecological environment and promote county-level economic growth is of considerable theoretical and practical significance. Using panel data for 744 county-level administrative units in the Yangtze River Economic Belt from 2007 to 2023, this study treats the designation of National Leisure Agriculture and Rural Tourism Demonstration Counties as a quasi-natural experiment and employs a staggered difference-in-differences approach to examine the impact of agritourism integration on the synergistic development of carbon reduction, pollution control, green expansion, and economic growth at the county level. The results show that: 1) designation as a demonstration county significantly enhances the synergistic development of carbon reduction, pollution control, green expansion, and economic growth. This finding remains robust after a series of tests, including parallel-trend and dynamic-effect analyses, placebo tests, matching analysis, heterogeneous treatment effect tests, and double machine learning-based causal inference. 2) Mechanism analysis suggests that green technological innovation, industrial structure upgrading, and strengthened environmental regulation are potential channels through which agritourism integration promotes county-level synergistic development. 3) Heterogeneity analysis shows that the positive policy effects are mainly concentrated in counties under non-old-industrial-base cities, counties outside major grain-producing areas, and counties under key environmental protection cities. These findings provide county-level empirical evidence for evaluating the integrated ecological and economic effects of agritourism integration policies. They also offer policy implications for the Yangtze River Economic Belt to promote the value realization of agricultural and tourism resources and the synergistic governance of carbon reduction, pollution control, green expansion, and economic growth in accordance with local industrial foundations, agricultural functional positioning, and environmental governance conditions.