Purpose: To deepen our understanding about the development of team performance, the purpose of this paper is to develop a model that explains how ambidexterity and ethical leadership affect knowledge sharing and team performance through within-team competition. Design/methodology/approach: This study demonstrates the applicability of ambidexterity and within-team competition by surveying 78 teams from the high-tech and banking industries. This study further presents a three-way interaction among ambidexterity, politics and job complexity. Findings: This study finds that both ambidexterity and ethical leadership are positively related to knowledge sharing and team performance through the mediation of team development competition. Originality/value: This study confirms that ambidexterity and ethical leadership play critical factors for improving knowledge sharing and team performance through the mediation of team development competition. Furthermore, the moderating effects of politics and job complexity are also confirmed in the research.