This article considers the issue of implementing a model of blended learning to prepare master students majoring in Mathematics (speciality code in Ukrainian educational system ”014 Secondary Education. Mathematics”). The research analyses the existing developments of the issue about the use of blended learning while training would-be mathematics teachers. The researchers determined and explained the stages of work on developing the online course ”Methods for Teaching Mathematics to Students at Technical Universities”, that is used when students learn methodological subjects of the curriculum. The research describes the development of the theoretical online course model and methodological recommendations on the learning materials and preparing papers for the course. The article offers recommendations related to the course structure. The course developers defined the usability criteria of the educational platforms, determined the stages of course users’ activity, their content, and organization. The research describes the areas of online course activity management, the course tutors’ and moderators’ teamwork is defined as the main condition of its development and support. In order to prove the efficiency of implementing blended learning of the methodological subjects, an experiment was carried out during the assistant practice in technical universities that master students of the specialization ”Mathematics” had. The results allowed confirming the efficiency of students’ practical training during blended learning of the methodological subjects that in its turn encouraged the improvement of the assistant practice results.