In this paper we examine the effects of different competitive conditions on the determination and evaluation of strategies of corporate social responsibility (CSR). Although the mainstream of current thinking in business ethics recognizes that a firm should invest in social responsibility, the normative theory on how specific competitive conditions affect a firm’s social responsibility remains underdeveloped. Intensity of competition, risks to reputation and the regulatory environment determine the competitive conditions of a firm. Our central thesis is that differential strength of competition produces differential moral legitimacy of firm behavior. When competition is fierce or weak, different acts or strategies become morally acceptable, as well as economically rational. A firm has to develop its own strategy of social responsibility, in light of its competitive position, as well as ethical considerations.