This paper investigates the health effects of the introduction of a near universal paid parental leave (PPL) scheme in Australia, representing a natural social policy experiment. Along with gender equity and workforce engagement, a goal of the scheme (18 weeks leave at the minimum wage rate) was to enhance the health and wellbeing of mothers and babies. Although there is evidence that leave, especially paid leave, can benefit mothers' health post-partum, the potential health benefits of implementing a nationwide scheme have rarely been investigated. The data come from two cross-sectional surveys of mothers (matched on their eligibility for paid parental leave), 2347 mother's surveyed pre-PPL and 3268 post-PPL. We investigated the scheme's health benefits for mothers, and the extent this varied by pre-birth employment conditions and job characteristics. Overall, we observed better mental and physical health among mothers after the introduction of PPL, although the effects were small. Post-PPL mothers on casual (insecure) contracts before birth had significantly better mental health than their pre-PPL counterparts, suggesting that the scheme delivered health benefits to mothers who were relatively disadvantaged. However, mothers on permanent contracts and in managerial or professional occupations also had significantly better mental and physical health in the post-PPL group. These mothers were more likely to combine the Government sponsored leave with additional, paid, employer benefits, enabling a longer paid leave package post-partum. Overall, the study provides evidence that introducing paid maternity leave universally delivers health benefits to mothers. However the modest 18 week PPL provision did little to redress health inequalities.