The features of the physical environment can influence children cognitive, affective and social development. This is true also in educational settings, where the physical environment acts as a third teacher, in addition to the educator and the peers. Empirical research in environmental psychology has mainly investigated the role of the physical environment on children behaviour in primary and secondary schools, while less attention has been devoted to the analysis of child-care centres.This study investigates the effects of a specific environmental feature of child-care centres, namely the presence of natural space, on children well-being. A consistent bulk of research has shown that contact with nature promotes many beneficial outcomes. Among the others, psychological restoration, namely the recovery of an effective cognitive functioning and the reduction of stress level. In addition, nature can promote positive social interaction. In this study, we tested the hypotheses that contact with nature in child-care centres promotes psychological restoration and increases the quality of children’s social interaction. Children’s performance in structured activities and behaviour in free play after time spent in indoor space vs. outdoor green space were compared, controlling for several confounding variables (e.g. environmental quality of the indoor and outdoor space and classroom density).Results of a pilot study in a child-care centre in Rome, Italy, attended by 16 children (age range 18-36 months) suggest that contact with outdoor green space reduces stress levels and positively influence both children’s performance in a visual-spatial task and social behaviour. The main study involved 39 children (age range 18-36 months) attending three different child-care centres. Observations of children behaviours, with specific reference to attention in the activity performed, stress levels and quality of social interaction, were made in a longitudinal design during daily activities in the day-care centres.Results showed the positive effects of contact with nature on children’s cognitive functioning, stress reduction, and quality of social interaction: no significant difference in the dependent variables emerged in the activities before free play; conversely, after free play in the outdoor green vs. indoor space children showed more focused attention in the performed activity, reduced stress levels, and more positive social interaction. A further study in another child-care centre, in which more structured measures of the dependent variables were included (e.g., a cognitive test of attention) confirmed the positive effect of contact with nature for children in child-care centres.