Shared leadership is a dynamic and emergent phenomenon in teams, in which leadership is shared among team members to facilitate a team’s goal achievement. It is an informal process in which team members influence one another to assume or relinquish leadership roles to enhance task accomplishment and achieve team goals. Shared leadership is a beneficial form of horizontal leadership that complements vertical leadership practices in teams, as it is associated with improved team performance. This dissertation explores the emergence, development, and consequences of shared leadership in project teams. Despite the vast body of research on shared leadership, project teams as a research context have received less attention, but interest is increasing. Project teams differ from other teams because they are temporary constructs operating in uncertain environments and performing complex and unique tasks. This research comprises three empirical studies, two of which employ a retrospective, qualitative approach, while one adopts a longitudinal, quantitative approach. The first study focused on project team members’ perceptions of project life-span events that triggered or hindered the emergence of shared leadership. The qualitative research identified the events through activity theory and analyzed their role in the emergence of shared leadership. The second study explored the development of shared leadership over one year by tracking changes across four timepoints. Besides shared leadership change, the study explored the associations among shared leadership, role clarity, and organizational support. The third study investigated the consequences of shared leadership on team members’ job demands and resources. The qualitative study explored team members’ experiences of the consequences of shared leadership through the lens of the job demands-resources theory (JD-R). The findings showed that different events throughout the project lifespan are important triggers of shared leadership in project teams. The project work, as such, is characterized by specific events, such as approaching deadlines and milestones, which can serve as venues for sharing the emergence of team leadership. Unexpected events, such as changes in team composition, triggered the emergence of shared leadership. Besides events, shared leadership emergence requires team member traits such as competence and experience, as well as team members’ perceptions of clear roles and project goals. Regarding changes in shared leadership over project progress, this study found that shared leadership remained stable during a one-year follow-up. Role clarity was found to be associated with shared leadership. The findings showed that team members experienced that job demands and resources increased due to shared leadership. Team members perceived that shared leadership increased undesirable demands when leadership was shared, but team member roles and the goals of work remained unclear. Conversely, shared leadership was experienced as increasing job demands, which were later rewarded by personal growth and learning. Shared leadership was perceived to enhance team members’ personal and job resources. Besides this, shared leadership was experienced to enhance job resources at the project team level. The findings highlight the importance of events in the project lifespan in the emergence of shared leadership. Project work, as such, embeds multiple events that facilitate the emergence of shared leadership. Shared leadership seems to remain rather stable throughout the project’s progress, and it was experienced to increase the project team members’ job demands and resources. The findings expand the understanding of shared leadership emergence, development, and consequences in project teams, contributing to shared leadership and project leadership research streams.