The restorative power of nature has long been recognized in environmental psychology, particularly for its role in enhancing cognitive function and emotional well-being. This study investigates how biophilic outdoor play environments can influence the health and restorative experiences of preschool children aged 4 to 5 years. Employing a comparative case study methodology, the research was conducted at two licensed childcare centers in Iran one featuring a biophilic outdoor design and the other a conventional playground setting. Data were collected through field observations, semi-structured interviews, spatial mapping, and a perceived restorative experience questionnaire adapted for young children. The findings demonstrate that children in biophilic play settings showed greater interaction with natural elements, engaged in more diverse and imaginative play, and exhibited significantly higher levels of perceived restoration. These results support Attention Restoration Theory (ART) and highlight the relevance of biophilic design principles—such as vegetation, topographical variation, and natural loose parts—in supporting children's emotional recovery and mental focus. The study contributes to a growing body of evidence advocating for nature-integrated environments in early childhood education. It offers practical design guidelines for architects, educators, and policymakers aimed at enhancing the developmental potential of outdoor environments. By promoting multisensory and ecologically rich play experiences, biophilic design holds the promise of nurturing healthier, more resilient children. The study also identifies areas for future research, including longitudinal analysis and broader cultural applicability.