The article contains the results of scientific research on the process of building ecological competence of schoolchildren on the basis of axiology. The analysis of the integrated educational process in general secondary and out-of-school education institutions through their transversal ecologization has been carried out. A number of social reasons that determine the urgency of these issues has been characterized. The definition of the term "environmental competence of students" has been defined as awareness of the ecological foundations of nature management, the need to protect nature, compliance with the rules of behavior in nature, economical use of natural resources, understanding of the context and relationship of economic activity and the importance of nature conservation to ensure the sustainable development of the society. The analysis of the legislative field on determining the axiological basis for building environmental competence of schoolchildren, particularly through the provisions of the Law of Ukraine "On Education" and the State Standard of Basic Secondary Education has been carried out. The formation of the concept of "value" in certain periods of development of educational process subjects has been studied. The axiological principles of building ecological competence of schoolchildren have been determined, the significance of upbringing as an integral part of the educational process has been revealed. The methodology of determining the content (environmental knowledge, skills, personal willpower), establishing forms (forms of general secondary education, forms of extracurricular education) and methods (organization and implementation of educational and cognitive activities, active learning, control and self-control, stimulating learning activities), building ecological competence of schoolchildren has been created. It has been proved, that the social effect of qualitative building of environmental competence of schoolchildren will be manifested in improving their nearest environment; upbringing conscious, ecologically competent citizens able to think critically and make competent decisions about the environment; actualizing socially significant functions of education; increasing social cohesion around environmental issues; promoting social formation of schoolchildren