The premise of parent‐centred programmes for parents of anxious children is to educate and train caregivers in the sustainable implementation of cognitive behaviour therapy (CBT) in the home. The existing operationalization of parent involvement, however, does not address the systemic, parent or child factors that could influence this process. The qualitative approach of grounded theory was employed to examine patterns of action and interaction involved in the complex process of carrying out CBT with one's child in one's home. A grounded theory goes beyond the description of a process, offering an explanatory theory that brings taken‐for‐granted meanings and processes to the surface. The theory that emerged from the analysis suggests that CBT implementation by mothers of anxious children is characterized by the evolution of mothers' perception of their child and mothers' perception of their role as well as a shift from reacting with emotion to responding pragmatically to the child. Changes occur as mothers recognize the crisis, make links between the treatment rationale, child's symptoms and their own parenting strategies, integrate tenets of CBT for anxiety and eventually focus on sustaining therapeutic gains through natural life transitions. The theory widens our understanding of mothers' role, therapeutic engagement, process, and decision‐making. The theory also generates new hypotheses regarding parent involvement in the treatment of paediatric anxiety disorders and proposes novel research avenues that aim to maximize the benefits of parental involvement in the treatment of paediatric anxiety disorders. Copyright © 2016 John Wiley & Sons, Ltd. Key Practitioner Message Mothers of anxious youth who take part in parent‐centred programmes experience a shift in their perception of the child and of their role. Parental strategy after CBT implementation shifts from emotional empathy to cognitive empathy. Mothers experience significant challenges and require additional support in prevention of relapse and knowledge translation.