The aim of the paper is to analyze the concept and structure of a biology teacher’s mathematical competence. In the research described in this paper, theoretical methods of systems analysis, theoretical modeling of pedagogical process, superficial peer review, and sampling methods are used. The nature of a biology teacher's activity made it possible to identify 21 areas of mathematical activities; peer rating thereof was conducted; three mathematical competence levels (Elementary, Intermediate, Advanced) were identified. According to the developed model, mathematical competence includes blocks of subject-methodological and scientific analytical activities of a biology teacher, blocks of analytical, operational and gnoseological functions, a block for selecting mathematical activity types, a core and a block of secondary types of activities. Estimates of complexity of main types of mathematical problems for biology teachers were also obtained and key problem types were identified: operation problems on fractions and decimals, standard index form, and division in a given ratio, combinatorial, probabilistic theoretical problems, and data analysis problems. The research conducted makes it possible to develop a methodological mathematical competence development system in the continuing postgraduate pedagogical education system and improve the level of mathematical training of future biology teachers at pedagogical universities. Developed mathematical competence of a biology teacher enables quality teaching of the corresponding subject taking into account key interdisciplinary relationships. Further research in this area includes detailing the structure and content of a biology teacher’s mathematical competence, study of the correlation between mathematical competence levels and other components of a biology teacher’s subject-methodological competence, and development of methodological systems for developing a biology teacher’s mathematical competence in the postgraduate pedagogical education system