Green finance is increasingly important in both academia and industry, yet the relationship between green bonds and bank loans remains largely understudied. In this study, we conduct an empirical investigation into the impact of the credit spreads of green bonds on the structure of debt financing. Our findings suggest that companies with larger credit spreads on green bonds in the secondary market tend to experience a higher growth rate in new bank loans. The presence of such credit spreads in the secondary market exacerbates corporate financing constraints and information asymmetry. This dynamic fosters implicit collusion between enterprises and banks, enhancing the firms' ability to secure bank loans. This research sheds light on the economic implications of the credit spreads of green bonds from the banks' perspective and offers valuable insights for optimizing credit strategies and detecting greenwashing behavior among banks and investors. •We examine the impact of green bond spreads on firm-level bank loans in China.•Firms with larger green bond spreads tend to have higher growth rates of new bank loans.•Large credit spreads exacerbate firms' financing constraints and information asymmetry.•These effects depend on the corporate ownership and holding structure.