The object of the study is the methodology of teaching Russian morphology at secondary school. The subject matter of the research is the teaching potential of morphology for building a system of skills necessary for speech activity and the development of learners’ systematic thinking. The study aims to search for methodological factors that can enhance learners’ mental activity in the process of mastering the morphology of the Russian language. Theoretical research methods (analysis, synthesis, systematisation, generalisation of results) in conjunction with practical research methods (modelling the process of teaching morphology, learning process observation) are employed in the study. The paper examines theoretical sources, practices in teaching morphology at school and suggests ways to reverse negative trends in education. The relevance of the problem is highlighted, in the first place, by the fundamental importance of morphology for learners’ personality development. Secondly, it is emphasised by the fact that modern school-leavers lack the system of morphological skills. Lastly, negative trends in teaching this branch of linguistics as part of the school Russian course persist, which also underlines the relevance of the research. The study focuses on the theoretical aspects of the addressed problem and takes into consideration modern knowledge of psychology, psycholinguistics, linguistics, the methodology of teaching Russian. Additionally, the paper presents methods and techniques of teaching such difficult morphological topics as «The Pronoun», «The Participle», «The Numeral». It is concluded that problem-based learning is effective as its implementation will enable teachers to enhance their students’ mental activity in the process of cognition and optimise the outcomes of teaching Russian morphology at secondary school.