The aim of this study was to examine whether the availability of affordances in preschool outdoor environments influences children's social play. Participants were 173 children aged between 3 and 6 years (M = 3.95, SD = 0.82) who were attending a total of 18 early childhood education centers in the Basque Country (Spain). The results indicate that low availability of affordances in the preschool outdoor environment has a negative impact on children's group social play. Based on application of the Affordance Scale [Kyttä, Marketta. 2002. "Affordances of Children's Environments in the Context of Cities, Small Towns, Suburbs and Rural Villages in Finland and Belarus." "Journal of Environmental Psychology" 22 (1-2): 109-123. doi:10.1006/jevp.2001.0249] we propose a cut-off score for identifying environments that are likely to discourage social play. In light of the results obtained we believe that the educational community should consider the concept of affordances in order to ensure that the features of preschool outdoor environments promote a variety of social play activities.