The potential benefits of teacher leadership are widely acknowledged; however, the conceptualization of this construct is in need of theoretical development and analytic clarification. The purpose of this mixed methodology study was to operationalize distinct types of teacher leadership into an organized typology, based on case studies of teacher leaders in a science education project. In addition, through confirmatory factor analysis, evidence for factors representing the distinct types of teacher leadership identified in the typology were found in a general teacher leadership survey. Implications for teacher leadership research and practice are discussed.