In contrast to the conventional fund management industry with a profit-oriented logic based on risk and return, ethical and faith-based funds should follow the religious principles of their investment-style philosophy. Islamic funds should obey the theological teachings of the primary sources of Islam, the Quran and Sunnah, as stakeholders expect these religious teachings to influence the investment decisions of fund managers. In practice, Islamic fund managers use Accounting and Auditing Organization for Islamic Financial Institutions ’s screening criteria, based on secondary (...) sources of Islam, which allow investments that are only partially halal to be included in their portfolios. This study finds that a more religious logic in screening practices, although impairing diversification, does not necessarily harm performance. Thus, Islamic investment funds, and the wider ethical fund management industry, should, and could, adopt stricter screening criteria that match their investment mandates and bring more ethical business practices to the industry. (shrink)