The goal of this study was to examine the effects of preterm birth and maternal childbirth‐related posttraumatic stress and parenting stress on maternal mind‐mindedness (MM). The study also investigated the effects of perceived social support on parenting stress and MM. Sixty‐five preterm (N = 32) and full‐term (N = 33) mother–infant dyads were observed at 6 months. Measures of maternal MM were obtained from observations of mother–infant interaction. Mothers also provided ratings of their posttraumatic stress disorder (PTSD) symptoms, parenting stress, and perceived social support via an online survey. Experiencing a preterm birth did not affect mothers’ use of mental state descriptors during mother–infant interaction. Neither childbirth‐related posttraumatic stress nor parenting stress directly affected maternal ability to comment on the child's mental states appropriately. However, at medium and high levels of perceived social support, a negative association between parenting stress and MM was observed. Maternal perception of being emotionally supported by significant others promoted MM in mothers showing low or mild levels of parenting stress, but not in mothers experiencing high stress in parenting their infants. Results suggest that a proclivity to MM might be affected by the interaction between parenting stress and social support, rather than by childbirth‐related variables, such as prematurity.