This article explores children's self-initiated outdoor play and holistic learning in a Norwegian kindergarten. While children's self-initiated play is valued in Nordic ECEC, it is rarely analyzed in relation to holistic learning. To explore how children's self-initiated outdoor play contributes to children's holistic learning in ECEC, we observed a group of twenty-four-five-year-old children during outdoor play in a Norwegian kindergarten, taking field notes and photographs. We analyzed it with a biosocial approach, where learning is understood as produced through an assemblage of social and biological forces. We found that with a creative and imaginative attitude, children sought intense and novel physical experiences and interactions with each other, other species, and things, while also navigating rules, relationships, and their own and others' emotions. We discussed the strategies we observed in relation to 'indirect pedagogy' and teacher-led pedagogy, challenges relating to risk, and young children's opportunities for holistic learning through self-initiated play in ECEC.