To provide inclusive education to autistic students, it is important that teachers possess knowledge about autism, feel competent in teaching autistic students, and have a positive attitude toward the inclusion of autistic students. In this study, we explored knowledge, self-efficacy, and attitude concerning autism among N = 887 teachers in Germany. The results showed that knowledge about autism was only moderate and teachers held some typical misconceptions about autism. Moreover, teachers did not possess overwhelmingly high self-efficacy beliefs whereas their attitude toward inclusion of autistic students was rather positive. Experience with teaching autistic students was associated with more knowledge and higher self-efficacy. Also, female teachers were more knowledgeable about autism and felt more competent in teaching autistic students than male teachers. However, the type of school where teachers were working made hardly any difference in their knowledge, self-efficacy, and attitude. Overall, the results suggest that teachers in Germany need more autism training to increase their knowledge about autism and their self-efficacy beliefs in teaching autistic students.