The goals of this study were to investigate (a) the dyadic relations of mothers' and children's perceptions of children's anxiety symptoms across development, (b) whether maternal perceptions of children's anxiety serve as a mediator of the association between maternal anxiety and child anxiety, and (c) whether sensitive/structured parenting moderates these processes. Participants were 180 mother-child dyads (96 female) recruited from Quebec, Canada, and assessed in preschool, middle childhood, and early adolescence. Mothers and children completed questionnaires on children's anxiety, and mothers additionally completed a questionnaire on their own anxiety. Maternal sensitivity/structuring was assessed from an observed interaction task. Results from an actor-partner interdependence model suggest (a) maternal perceptions of children's anxiety in middle childhood predict children's self-perceptions in adolescence, but not vice versa; (b) maternal perceptions in middle childhood mediate the link between maternal anxiety in early childhood and child self-perceptions of anxiety in adolescence; and (c) the indirect effect of maternal perceptions is moderated by maternal sensitivity/structuring such that mothers who perceived more anxiety in their children and who were observed to show lower levels of sensitivity/structuring in middle childhood tended to have children who perceived more anxiety in adolescence. Findings suggest that maternal awareness of children's anxiety may be one mechanism, in the presence of relationships characterized by lower levels of sensitivity, through which anxiety risk is transferred from parent to child over time. Public Significance StatementThis study suggests that a mother's awareness of their child's anxiety predicts how their child comes to see their anxiety across time, but not vice versa. Anxious mothers see more anxiety in their children and, when they are less sensitive and supportive, have children who perceive experiencing more anxiety. This highlights the importance of targeting parent-child communication about emotions when seeking to understand and intervene in children's anxiety.