In the current study, we draw on the original job characteristics model (JCM) and on an elaborated model of work design to examine relationships between ethical leadership, task significance, job autonomy, effort, and job performance. We suggest that leaders with strong ethical commitments who regularly demonstrate ethically normative behavior can have an impact on the JCM elements of task significance and autonomy, thereby affecting an employee's motivation (willingness to exert effort), which in turn will be evidenced by indications of enhanced task performance and organizational citizenship behavior. We conducted a field study by surveying pairs of co-workers in a diverse set of organizations. Results provide support for a fully mediated model whereby task significance and effort fully mediate relationships between ethical leadership and subordinates' job performance. Implications for future research on job design are discussed. Copyright © 2010 John Wiley & Sons, Ltd.