The article considers the development of the online educational model “Creative Thinking through Learning Elementary Maths” and the results of the effciency to implement this course for students of the specialization “Mathematics” while learning Elementary Mathematics. The research represents the development of learning materials for the online course posted in free access on the educational platform “Higher School Mathematics Teacher”. The course components (theoretical, practical, and feedback) are focused on the organization of motivated and consistent students’ activity; open and integrative Rich tasks of three levels of complexity. The course participants’ activity, focused on the recognition, classification, solution, creation of Rich tasks, encourages the formation of the main components of creative thinking that include a problem statement, fluency, flexibility, originality, and elaboration. The first version of the course materials was improved following course users’ wishes, and then the effciency of online course education was checked using an experiment. The analysis of results of the experiment allows concluding about the effciency of the developed model of learning an online course.