Postpartum depression (PPD) is the most common complication of childbearing, and recent studies have attempted to examine risk factors associated with it. The main study hypothesis was that a protective situational factor at a sensitive time period (full rooming‐in postpartum) would moderate the associations between insecure attachment dimensions and PPD. Three hundred twelve women, in either full or partial rooming‐in, participated in a longitudinal study at the maternity ward of a tertiary healthcare center. A Demographic questionnaire and the Experiences in Close Relationships Scale were administered at 1–4 days postpartum, and the Edinburgh Postnatal Depression scale at 2 months postpartum. PPD was significantly associated with both anxious and avoidant attachment dimensions, but not with rooming‐in conditions. In addition, women in partial rooming‐in showed a positive correlation between insecure attachment dimensions and PPD, whereas no such correlation was found for full rooming‐in women. A situational factor such as full rooming‐in, which occurs at a critical time point for the mother–infant relationship, can moderate the association between maternal avoidant or anxious attachment dimensions and the mother's PPD levels. Postpartum practices, such as rooming‐in, can be personalized and thus beneficial in moderating personal risk factors for PPD.