Teaching mathematics while learning from students' mistakes, errors and misconceptions, is most important for meaningful learning. This study was based on intervention programs prepared by preservice teachers. It aimed to examine their knowledge of assessment of errors in mathematics amongst pupils with learning disabilities, and their use as a basis for didactically adapted teaching. The research methodology was qualitative. Three pairs of preservice teachers (a total of six students) studying special education participated. Content analysis was performed using the Individualized Education Program and according to Hiebert and Lefevre's cognitive learning model. The research findings support and indicate the importance of coordinating an analysis of the pupil's errors and the choice of a didactically adapted teaching strategy, in order to achieve a more effective focus on the mathematical difficulties and the misconceptions, and thus to contribute to improving the therapeutic effectiveness and realize the student's abilities to the maximum. The current study is thus innovative in examining the assessment of the errors in mathematics made by students with learning disabilities, not only in regards to the disability in cognitive functioning and difficulties in mathematical functioning, but also in regards to the use of conceptual and procedural mathematical knowledge by the preservice teachers and the teacher.