In today’s society, ethics and corporate social responsibility are again rated high on the corporate agenda of many firms. Ethical codes, based on corporate values, are used to guide the behaviour of employees. However, research results related to the effectiveness of these codes are scarce and inconsistent. Moreover, research is mostly us-based. This study examines the effectiveness of both ethical and professional codes in the dutch management consulting industry. The results reveal that the presence of an ethical code has a negative effect on individual ethical decision-making. The enforcement of compliance with professional codes is—in an indirect way—positively associated with the organisation’s ethical climate.