This article explores the relationship between contact with nature in childhood and adult personality. An international sample of 783 participants from 42 countries reported on their frequency of contact with specific natural environments in childhood and adulthood, and completed measures of adult personality and socio-demographic details. Multivariate regression, canonical correlations, and least-squares path analyses were employed to identify relationships between variables. Contact with nature in childhood predicted higher Openness and lower Neuroticism. In particular, more frequent contact with forest environments in childhood was correlated with facets of Openness (Creative Imagination, Intellectual Curiosity) and Neuroticism (Anxiety, Depression). Mediation analyses indicated that engaging in contact with nature in childhood may represent a learned emotional regulation strategy that results in lower Neuroticism when continued in adulthood, while natural environments may be an ideal environment for creative play in childhood that predicts higher Openness in adulthood. This study makes a contribution to the field by describing the impact, and possible mechanisms, of contact with natural environments in childhood on adult interpersonal behaviours, which may assist in the design of environments that are best suited for restoration and play.