Access to green space (GS) is vital for children’s health and development, including during daycare. In Japan, deregulation to alleviate daycare shortages has created a new category of so-called unlicensed daycare centers (UDCs) that often lack dedicated GS. UDCs rely on surrounding GS, including parks, temples and university grounds, but reports of conflicts highlight the precarity of children’s well-being in a rapidly aging country. Knowledge about GS access in Japanese UDCs remains scarce. Our mail-back survey (n = 173) of UDCs and online survey (n = 3645) of parents investigated threats to GS access during daycare across 14 Japanese cities. Results suggest that UDCs use a variety of GS and aim to provide daily access. Caregivers are vital in mediating children’s access, but locally available GS diversity, quality and quantity as well as institutional support were perceived as lacking. Parents did not rank GS high among their priorities when selecting daycare providers, and showed limited awareness of conflicts during GS visits. Implications of this study include the need for caregivers and parents to communicate and collaborate to improve GS access, and the importance of strong public investment into holistically improving GS diversity, quality and quantity from the perspective of public health and urban planning. View Full-Text