This study aims to explore the influence of outdoor teaching among students, aged 13, on arithmetic performance and self-regulation skills as previous research concerning outdoor mathematics learning is limited. This study had a quasi-experimental design. An outdoor and a traditional group answered a test and a self-regulation skills questionnaire before and after a 10 weeks unit in arithmetic. Findings suggest differences in changes in academic performance between the groups in favour of the outdoor group and no significant changes in self-regulation skills, apart from a decrease in intrinsic motivation in the traditional group.