Objectives: Many European countries face challenges in long-term care for older people, such as the growing number of older people requiring care, the increasing complexity of their health care problems, and a decreasing workforce that is inadequately prepared. Optimizing the staff and skill mix of health care teams may offer part of the solution for these challenges. The aim of this study was to obtain insight into the development of teams in terms of staff and skill mix, and the influence of staff and skill mix on quality of care, quality of life, and job satisfaction. Methods: Seven teams in elderly care in the Netherlands participated in this exploratory case study. From April 2013 to January 2015, a researcher followed the development of the teams, performed observations at the workplace and held interviews with team members, team captains, and (representatives of) clients. Data-analyses were carried out in MAXQDA 11, by coding interviews and analyzing themes. Results: During the project, almost all teams became more diverse in terms of staff and skill mix. In general, there was a trend towards adding (more) higher-qualified health care workers (e.g. nurse) to the team, increasing communication with other disciplines, and enhancing skills of lower-qualified team members. A more diverse staff and skill mix had a positive effect on quality of care and quality of life of clients, and on job satisfaction, but only under certain contextual conditions. Important contextual conditions for successful functioning of a diverse team were a shared view of care by all team members, good communication, autonomy for professionals, and a safe team culture. Conclusion: A more diverse staff and skill mix, in combination with positive contextual conditions, can result in improved quality of care, quality of life, and job satisfaction. However, a "one size fits all" blueprint for the optimal staff and skill mix, that suits each team and organization, does not exist. This depends on the context, and should be based on the needs of the clients and possible future changes in these needs.