The overall aim of this study is to examine why outdoor education is not implemented as a method of practice to a greater extent by teachers’ who work with natural science topics based on guidelines from the school's mission. The method used in this study is interviews with natural science teachers in grades 1-3. The results have been analyzed accordingly to the theory of implementation containing three keywords: understanding, will and ability. The result shows that the teachers have a deep understanding of using outdoor education in their learning activities and a positive will in implementing outdoor education in their teaching. However, the study also shows that there were some practical obstacles such as lack of time for planning and resource issues and also possible shortcomings in teachers' subject knowledge and educational skills that can be considered as challenges in the performance of outdoor education.