AIM:To investigate the relationship between maternal mindfulness and maternal anxiety 1 month after childbirth. METHODS: A cross-sectional design was used, featuring anonymous questionnaires that were completed between July and December 2014 at two Japanese hospitals. The participants (n = 151) completed the Mindful Attention Awareness Scale (Japanese version) and the State-Trait Anxiety Inventory Form X (Japanese version). The data analysis was carried out by using a hierarchical multiple regression. RESULTS: The state and trait anxiety scores showed significant relationships with mindfulness, the mother's age, and the perceived difference between the expectations of motherhood before childbirth and the reality of post-partum daily life. Furthermore, the amount of average sleep time in the past week (including naps) showed a negative association with the state anxiety score, whereas the marital relationship showed a positive association with trait anxiety. Finally, at 1 month post-partum, the mothers with greater mindfulness scores showed lower anxiety. CONCLUSIONS: Improvements in mindfulness could help mothers to reduce their post-partum anxiety.