Teamwork is one of the most important factors for business success in the modern economy. In almost every area of business, teams receive more and more attention, since it has been found that teamwork leads to greater individual, group, and even organizational performance. The aim of this research is to investigate the effectiveness of teamwork and its relationship with team performances. Specifically, the authors tried to investigate which factors of teamwork effectiveness have a positive relationship with teamwork performance and the sustainability of teams in the future. The subject of the research is the effectiveness of teamwork as a construct that is widely presented in the scientific field of organizational behavior and human resource management, but is still underexplored in empirical research, especially in the banking sector. An investigation with a self-audit questionnaire on teamwork effectiveness was conducted on a sample of 401 employees in the banking sector in Serbia, in 16 out of the 26 existing banks in the country. The authors used SmartPLS software in order to test the questionnaire (indicator loadings, internal consistency reliability, convergent validity, and discriminant validity) and proposed research question (PLS-SEM). The results showed that factors such as innovative behavior of the team members, the quality of teamwork, and teamwork synergy have positive relations to teamwork performance. This paper contributes to the better understanding of the factors of teamwork effectiveness that contribute to team performances, with respect to the banking industry in Serbia. The limitation of the paper is the size of the sample, with respect to the total population.