Despite the benefits of nature play being widely recognized, parental restriction has become a significant barrier to children’s access to nature. To identify strategies against this trend, it is important to understand the factors that influence parental perception toward children’s nature play. We explored the impact of factors including parents’ childhood nature experience (CNE), nature relatedness (NR), urbanization degree, and socio-demographic characteristics using the results of an online survey of 516 parents in Japan. We found that most parents acknowledged the importance of nature, which was positively influenced by NR and CNE. Yet, parents expressed concerns about barriers, which were higher for mothers, urban residents, and people with lower CNE. There was a drastic generational increase in the restriction of children’s free play in nature. Parents’, especially mothers’ primary concern and the main contributor to their restriction, were incidents. Our study highlights the role of CNE and suggests that raising parents’ awareness and reducing their apprehension may be important approaches to encourage them to let children play in nature.