ABSTRACT This study investigated the associations between incarcerated mothers’ sensitivity and their co-residing children’s attachment security. Furthermore, the moderating role of children’s temperament on the associations between maternal sensitivity and children’s attachment security was examined. The study sample consisted of 84 incarcerated mothers (Mage = 29.9, SD = 5.6) and their 12- to 43-month-old (M = 25.3, SD = 8.3) children who co-resided with them in prison facilities. Maternal sensitivity and child’s attachment were assessed by observation of mother-child interaction using the Maternal Sensitivity Scale and the Turkish Toddler Attachment Sort-60, respectively. Mothers reported their children’s temperamental features (i.e. negative emotionality and effortful control) using the Early Childhood Behavior Questionnaire. Results showed that maternal sensitivity was related positively to children’s secure attachment and negatively to children’s disorganized attachment. Furthermore, children’s negative emotionality and effortful control moderated the associations between maternal sensitivity and children’s attachment. Specifically, maternal sensitivity negatively predicted children’s avoidant attachment only for children with low negative emotionality and with high effortful control. Additionally, maternal sensitivity negatively predicted children’s anxious attachment only for children with low effortful control. Results are discussed in terms of sample-specific experiences, contextual factors, and the differential susceptibility hypothesis.