This paper reports an exploratory case-study introducing a new method to quantify children’s social interactions during unstructured outdoor play. Movements of 18 children were tracked using wearable sensors over 20 sessions of outdoor play at school. Sessions were divided between two play conditions: Baseline; the usual play environment and Intervention; in which a playground intervention was implemented. Sensor data were used to build a network representing the social interactions that took place each day. Questionnaire-based measures of social and communication skills were completed by teachers, and peer nomination was used as a child-based measure of social skills.Social connectedness measured during outdoor play correlated positively with peer preference measures but not with teacher reported social skills. Social connectedness averaged over the 10 days of each play condition was not sensitive to between-condition differences. Findings are discussed qualitatively with reflections on measurement issues, implementation and ethics.