The present study examined the impact of teacher team composition on characteristics and attributes regarded as necessary for effective cooperative teaching. The study focused on potential differences between self-selected teacher teams and teams composed by the school administration. The central assumptions were that teachers working in self-selected teacher teams show more positive ratings of enjoyment, shared responsibility, job satisfaction and collective self-efficacy expectations than teachers who worked in institutionally composed teams. In order to investigate these hypotheses, an online survey was created. 321 language arts teachers participated in the survey. MANCOVA revealed significant differences in the dimensions 'shared responsibility' and 'enjoyment with the co-teaching process', where teachers from self-selected teaching teams showed significantly more positive ratings. These results support the assumption that self-selection of the team-mate is helpful for establishing compatible teaching teams, but does not necessarily lead to a higher quality of collaborative teaching.