This study investigates how green finance influences urban export technological complexity using panel data from 287 Chinese cities (2011–2024). Unlike previous research focusing on aggregate financial development, we construct a comprehensive green finance index and develop a theoretical framework demonstrating how green finance operates through dual channels: enhancing green innovation capacity and accelerating industrial structure upgrading toward knowledge-intensive sectors. Employing difference-in-differences and system GMM estimations, we find that green finance significantly increases export complexity, with a one-standard-deviation increase associated with 16% higher complexity. Effects exhibit substantial spatial heterogeneity, stronger in western regions and lower-tier cities where traditional finance falls short. These findings suggest green finance can simultaneously achieve environmental sustainability and trade competitiveness objectives, offering policy guidance for developing economies navigating green transformation while upgrading export structures.