Green finance is an important means to promote the construction of ecological civilization and plays an important role in promoting the coordinated governance of pollution and carbon reduction. Based on the panel data of 277 cities at or above the prefecture level in China from 2006 to 2021, this study calculates the development level of green finance and the synergistic efficiency of pollution and carbon reduction. In addition, this study constructs the driving distance matrix. The study uses the spatial Durbin model to conduct an empirical test on the spatial effect and transmission mechanism of green finance on the synergistic efficiency of pollution and carbon reduction. Results show that: (1) A significant spatial difference exists between the development level of green finance and the collaborative efficiency of pollution and carbon reduction in China from 2006 to 2021. Moreover, the high-value areas of the two are concentrated in the eastern and southeast coastal areas, respectively; (2) The development of green finance has a positive spatial spillover effect on the collaborative efficiency of pollution and carbon reduction. The conclusion remains after a series of robustness tests, that is, green finance has a significant positive promoting effect on the collaborative efficiency of pollution and carbon reduction between the city and its neighboring cities; (3) The development of green finance can promote the improvement of the collaborative efficiency of pollution and carbon reduction by improving the level of green technology innovation and the advanced level of industrial structure, that is, the two play an intermediary effect. The conclusions of this study provide experience for an in-depth understanding of the environmental governance effect of green finance and actively guide financial resources to participate in the collaborative governance of carbon pollution.