Courses and programs that teach ethics in business schools have long fallen short in promoting ethical decision-making and behavior. In this research, we further developed a teaching program based on moral identity principles by assessing its effectiveness in promoting students’ ethical decision-making and ethical behavior. Data were collected from 92 undergraduate marketing students undertaking the program in one week (one session) within a twelve-week teaching period. Results suggest that students who attended the teaching program based on moral identity principles reported greater levels of ethical decision making (post-test) and ethical behavior (delayed post-test) compared to those who attended the control program. Moreover, there was a marked improvement in the ethical decision-making of older as opposed to younger students. Theoretical and practical implications are discussed.