In this study, we propose and test a model of the effects of organizational ethical culture and organizational architecture on the perceived unethical behavior of employees towards customers. This study also examines the relationship between organizational ethical culture and moral acceptability judgment, hypothesizing that moral acceptability judgment is an important stage in the ethical decision-making process. Based on a field study in one of the largest financial institutions in Europe, we found that organizational ethical culture was significantly related to the perceived frequency of unethical behavior towards customers and to the moral acceptability judgment of this type of unethical behavior. No support was found for the claim that features of organizational architecture are associated with the perceived frequency of unethical behavior towards customers. This is the first study to document the differential effects of organizational architecture and organizational ethical culture on perceived unethical behavior of employees towards customers, in wholesale banking. Implications for managers and future research are discussed.