One key function necessary to successfully teach a heterogeneous student population is to individually adapt instruction to students' needs and prerequisites. Using structural equation modelling, the present study investigated whether or to what extent different factors, teachers' personal characteristics, their joint professional activities, and school-related framework conditions contribute to the implementation of teachers' self-reported adaptive instruction. For this purpose, teachers working in inclusive German schools (N = 471) were questioned. The instrument used to cover inclusive work was based on a multilevel concept oriented towards internationally well-established dimensions of inclusion. Moreover, personal characteristics and school-related parameters were covered. The key result revealed that the extent to which self-reported adaptive instruction is implemented by teachers depends, above all, on the teachers themselves, their characteristics, and their participation in joint activities. The structural framework, for example, school size or school type, did not play a considerable role. The contributing factors were discussed and implications derived.