Objective: The postnatal period can be both a rewarding and challenging time. Research has found that experiences of motherhood that are less positive than expected are associated with depressive symptoms, however, no known study to date has examined expectations across the separate domains of motherhood and how they impact on attachment. The aim of this cross-sectional study was to investigate whether discrepancies in a mother's expectations regarding their infant, levels of support, and sense of self and their actual experiences post birth impact on maternal feelings of attachment and depression in the postnatal period. Method: Two hundred and thirty-eight mothers in Australia (aged 19–44) who had given birth in the last 12 months voluntarily completed an online survey. Results: As predicted, results revealed that postnatal experiences that were less positive than expected regarding support and sense of self were associated with higher levels of depression and lower levels of attachment. Regarding infant expectations, experiences that were less positive than expected were associated with lower levels of attachment; however, experiences that were more positive than expected were, unexpectedly, associated with higher levels of depression. Conclusion: These findings highlight the importance of providing realistic expectations of motherhood through prenatal education and media messages to promote greater wellbeing and bond between mothers and infants which may maximise the chances of positive infant development.