Self-serving is defined as exhibiting self-enhancing perceptions, taking undue credit for success, avoiding due responsibility for failure, or making self-flattering presentations. As such, it is a bias indicating some distortion of reality either to the self or to others. A multi-level theory is offered which proposes that self-serving is functionally equivalent for individuals, groups, and organizations. Core causes of self-serving include identity protection and the pursuit or protection of material resources. Uncertainty and retroactive scrutiny are argued to exacerbate self-serving tendencies. Proactive scrutiny is expected to dampen these tendencies. Consequences of self-serving include the maintenance of deviant behavior, actor-observer conflict, and the acquisition of material and identity-related benefits. Self-serving is argued to be relevant to a wide variety of organizational phenomena at several levels, including performance appraisal, escalation of commitment, unethical behavior, intergroup conflict, institutional processes, and agency problems. The theory addresses several paradoxes of organizational life and several theoretical debates in the organizational sciences.