The essence of China's contemporary green economic transition is to enhance the capacity of the green production system, emphasizing regional technological and intellectual capabilities as the primary force of green economic growth (GEG). Economic complexity can reflect hidden regional production capacity, providing a new analytical tool for exploring GEG. Using a city–year panel dataset from 2000 to 2016, this study incorporates economic complexity and GEG into a unified research framework, adopting a fitness–complexity algorithm to measure Chinese urban economic complexity to empirically examine the influence and mechanisms of economic complexity on GEG. The results show that increased economic complexity promotes GEG by enhancing green technological innovation capacity and facilitating industrial structure upgrading, with one standard deviation increase in economic complexity followed by a 2.1% rise in GTFP. In addition, we emphasize the moderating effect of the government and the public, arguing that increased government environmental attention and public environmental concern reinforce the contribution of economic complexity. Finally, the findings reveal that public policies focusing on improving the economic complexity of low-complexity areas can strike a good balance between fairness and efficiency.