Research has shown that children experience increased emotional distress when engaging in emotional caretaking of a parent. The current study is the first to examine this process in families in which the source of the stress is the child's illness. Prospective associations were tested among mothers' depressive symptoms near the time of their child's cancer diagnosis, mothers' expressed distress and their child's emotional caretaking during an interaction task, and child anxious/depressed symptoms at 1 year postdiagnosis. Families (N = 78) were recruited from two pediatric hospitals soon after their child's (Ages 5-18) new diagnosis or relapse of cancer. Mothers reported on their own depressive symptoms and their child's anxious/depressed symptoms near the time of diagnosis or recurrence (Time 1) and 1 year later (Time 3). At Time 2 (4 months after Time 1), mother-child dyads completed a video-recorded discussion of their experience with cancer that was coded for observed maternal expressed distress (anxiety, sadness) and observed child emotional caretaking. Maternal expressed distress during the interaction was significantly related to more emotional caretaking behaviors by both boys and girls. Results of a moderated mediation model showed that child emotional caretaking at Time 2 significantly mediated the relation between maternal depressive symptoms at Time 1 and child anxious/depressed symptoms at Time 3 for girls but not for boys. The findings suggest that children's emotional caretaking behaviors contribute to subsequent anxious/depressed symptoms for girls, but not for boys, with cancer. (PsycINFO Database Record (c) 2018 APA, all rights reserved).