Growing body of research recognizes the importance of green spaces on the perinatal outcomes however, further evidence from different geographies are warranted. We aimed to investigate association between, and differential responses to, maternal exposure to green space and birthweight. Birth records (n = 82,221) were extracted from the Perinatal Data Collection (PDC) in Sydney's metropolitan area between January 2016 and December 2017. Association between green space quantity and birthweight, term birthweight, low birthweight, term low birthweight and preterm were assessed using linear and logistic regressions. Potential modification by area-level socioeconomic status and maternal country of birth were tested using interaction terms. Difference in birth weight for the ≥40% versus <20% green space within SA2s was 59.0 g (95%CI: 42.9, 75.3) in unadjusted models which dropped to 25.6 g (95%CI: 13.0, 38.2) in adjusted models. Stratified analysis suggested stronger associations for babies of mothers from affluent neighbourhoods, while statistically significant association was not observed in deprived areas. Furthermore, the association was more pronounced among babies to mothers who were born overseas. Associations were consistent for term births. Higher levels of green space were associated with lower odds of preterm birth in adjusted models. However, we did not identify statistically significant association between green space quantity and the risk of low birthweight (LBW). Our study suggests that green space may support healthier birth outcomes and help to reduce the birthweight gap between newborns of mothers born in Australia and overseas. However, disproportionate benefits among women in affluent neighbourhoods may widen socioeconomic inequities in birthweight. Living in greener neighbourhoods was associated with higher birthweight with stronger association among mothers lived in affluent areas and born overseas.