This study provides a theoretical background for collusion-induced overlending being the main cause of the 1997 Korean financial crisis. Our model consists of a lending institution, a borrowing chaebol of an unknown type, and an informed politician who can influence lending decision. We show that collusion can be formed between a low-type chaebol and the politician, and it may not be the lending institution’s best interest to deter such collusion. This equilibrium, however, is possible only when the economic environment is favorable. When the economy deteriorates, the expectations of the fall of the collusion equilibrium can trigger financial crisis. (JEL G30, D82, O16)