This study explores a phenomenon that has been shown to adversely affect managers' decisions-competitive irrationality. Managers are irrationally competitive in their decisions when they focus on damaging the profits of competitors, rather than improving their own profit performance. Studies by Armstrong and Collopy (1996) and Griffith and Rust (1997) suggest that the phenomenon is common but not universal. We examine the question of why some individuals exhibit competitive irrationality when making decisions, while others do not by focusing on four aspects of moral philosophy-deontological orientation, cognitive moral development, idealism, and relativism. Results suggest that individuals high in deontological orientation, high in cognitive moral development, high in idealism, and low in relativism will be less competitively irrational than those who are not.