Background: Most research on daughters of women with cancer have focused on the daughters' adjustment to the cancer with little attention given to the impact of the cancer on the relationships between mothers and daughters. Methods: Guided by the feminist relational‐cultural theory, this study examines mothers' perceptions of their cancer experience on their relationships with daughters, focusing on their emotional connections, ruptures or disconnections in the relationships, and relational competencies. By using the grounded theory, 29 in‐depth interviews of mothers with cancer were analyzed. Results: Although most of the participants reported closer relationships with their daughters as a result of the cancer experience, emotions such as fear, anger, or guilt were frequently cited. Mothers were able to work through these emotions with their daughters through four relational competencies: (a) anticipatory empathy (sensitivity about the impact of cancer on each other); (b) authenticity (full presence without fear of abandonment); (c) mutual empathy (caring and emotional support); and (d)mutual empowerment (capacity to empower one another). Conclusion: The concept of post‐traumatic relational growth is introduced to describe how mothers transformed the stressful experience of cancer into an experience in which they grew emotionally in relationship with their daughters. Copyright © 2013 John Wiley & Sons, Ltd.