This article describes a study devoted to the comparative analysis of modern requirements for a teacher-mentor and requirements for him in the works of an outstanding Russian teacher K.D. Ushinsky. The purpose of the study is to analyze the modern requirements for a teacher-mentor in comparison with the requirements of K.D. Ushinsky. The article reveals the stages of research: analysis of the works of K.D. Ushinsky «A guide to teaching on the «Native word», «The project of the teachers' seminary», «Preface to the first volume of «Pedagogical Anthropology», «Native word. A book for teachers», a comparative analysis of modern requirements for a teacher-mentor and the requirements for him by K.D. Ushinsky, generalization of research results and formulation of conclusions. The article reveals the stages of research: analysis of the works of K.D. Ushinsky «A guide to teaching on the «Native word», «The project of the teachers' seminary», «Preface to the first volume of "Pedagogical Anthropology», «Native word. A book for teachers», a comparative analysis of modern requirements for a teacher-mentor and the requirements for him by K.D. Ushinsky, generalization of research results and formulation of conclusions. The article analyzes the pedagogical works of K.D. Ushinsky and describes his requirements for a mentor as a teacher and educator, reveals the modern understanding of mentoring by the authors as professional support of a young (novice) teacher by a more experienced mentor colleague. K.D. Ushinsky in the «Guide to teaching on the «Native Word» imposes special requirements on the mentor – primary school teacher – awareness of mastering the native language, correct, literate speech, learning to understand oral and written speech, teaching students to express their thoughts in writing. In the «Teacher's Seminary Project», K.D. Ushinsky points out that a mentor should have not only professional knowledge, but also skills, as well as readiness to carry out his duties. According to K.D. Ushinsky, a teacher-mentor should have patience and special knowledge, as well as pedagogical tact and experience. K.D. Ushinsky places high demands on a teacher-mentor. His pedagogical ideas can be applied in the modern professional education of future teachers and in the mentoring activities of novice teachers.