The article discloses the contradictions, which define the necessity and possibility to use teacher's portfolio in the system of children's supplementary education. It gives the author's interpretation of the concept «supplementary education teacher's portfolio», defines objectives, the portfolio functions and the principles of its design. The article offers the author's structure of the supplementary education teacher's portfolio, which reflects the main directions of the teacher's professional activities, allows demonstrating the achievements and the results of these activities. The authors describe the alternatives to use the portfolio in supplementary education. The article reveals the risks of portfolio implementation in the institutions of supplementary education. Practical recommendations for the teacher's portfolio development given in the article are practiceoriented. The article addresses the administration and the teachers of the children's supplementary education institutions, the lecturers of the teacher's training colleges, who train future teachers of the supplementary education as well as the educators of the extended education within the process of the professional skills improvement for supplementary education teachers.