Background: Current evidence from studies on green space and child prosocial behaviour suggests a paucity of studies investigating the plausible role of green space quality in shaping the development of prosocial behaviour. This study aimed to examine longitudinal association between green space quality and prosocial behaviour among children. Methods: We analysed 10-year longitudinal data (2004–2014) from the Longitudinal Study of Australian Children (LSAC), a nationally representative cohort study. Prosocial behaviour that covers positive behaviours (e.g. sharing, helping) was measured using a prosocial scale from Goodman's Strengths and Difficulties Questionnaire (SDQ). Parents' perceptions on the availability of “good” parks, playgrounds, and play space in the neighbourhood assessed green space quality. Multilevel linear regression models were used to examine potential changes in prosocial behaviour across childhood in relation to green space quality. A two-way interaction term between green space and age was fitted to assess potential differences in the effect of green space quality by age. Sensitivity analyses by child's sex and history of residential movement were also performed. Results: From the analysis of 24,418 observations nested in 4969 children, prosocial behaviour was relatively high (mean = 8.13 out of 10; SD = 1.79) and about balanced proportions between girls (48.74%) and boys (51.26%) were included. Prosocial behaviour was higher among children whose parents agreed (β = 0.10; 95%CI = 0.04, 0.16) and strongly agreed (β = 0.20; 95%CI = 0.13, 0.27) to having quality green space in their neighbourhood. The benefit of exposure to favourable green space on prosocial behaviour was similar among both children who changed and did not change neighbourhood, but reported higher among boys than girls. Younger compared with older children or adolescents tended to benefit more by the presence of quality green space. Conclusion: Green space quality was positively associated with child prosocial behaviour. Boys and younger children tended to benefit more from quality green space. Future research might seek to identify preferred characteristics of quality green spaces, and to understand how these preferences vary by gender and age, to best support the development of prosocial behaviour across childhood and adolescence.