Family rituals serve important functions for families, especially at times of change and stress, such having a child diagnosed with cancer. No studies have investigated how family rituals may be impacted during pediatric cancer treatment. This qualitative study explored the impact of pediatric cancer and its treatment on family rituals. Semistructured interviews with 19 mothers of children with cancer, ages 8–17 years old, were conducted and analyzed using grounded theory strategies. The interviews revealed two main types of changes in rituals: Loss; and Transformation. The Loss of Family Rituals included two subcategories (Nonattendance at Ongoing Family Rituals, Disruption of Family Rituals). The Transformation of Family Rituals included three subcategories (Readjustment of Family Rituals, Creation of New Family Rituals, Reestablishing Old Family Rituals). Seven general functions of family rituals were identified (Celebrating, Family Cohesion, Family Communication, Respite, Sense of Predictability, Sense of Security, Rhythm of Life) and five illness-related functions (Grounding in Life, Hope, Marking the Course of Treatment, Sense of Normalcy, Treatment Adherence). Although pediatric cancer may compromise family rituals (nonattendance and/or disruption) and their functions, families develop adaptive strategies (readjustment, creation, and/or reestablish) to transform rituals and facilitate their potentially protective functions. Discussion of rituals can be integrated into interventions to optimize family interactions in the adverse context of pediatric cancer, via the readjustment of existing rituals, the creation of new ones and the reestablishing of old rituals.