Objective When a child is diagnosed with cancer, parents are faced with many practical and emotional challenges that can significantly affect their relationship. This study explores how having a child with cancer affects the quality of the parents' relationship, categorizes time points and events during the child's treatment when the relationship becomes most stressed and/or strengthened, identifies factors that help couples remain emotionally engaged throughout their child's cancer treatment, and assesses parental interest in a counseling intervention. Methods This is a cross‐sectional, multicenter study conducted via a semistructured self‐administered questionnaire that included the Revised Dyadic Adjustment Scale. Results One hundred ninety‐two parents of children diagnosed between the ages of 1 and 21 participated. Forty percent felt their relationship moved in a negative direction. Diagnosis and relapse of disease were cited as the most individually stressful time points in the disease trajectory, with hospitalizations and relapse being most stressful on the relationship. Participants felt most emotionally connected at diagnosis and least emotionally connected at the start and end of treatment. The majority of couples indicated interest in counseling to address ways to support their relationship. Soon after diagnosis and during treatment was reported as the preferred time to offer these interventions. Conclusion This study identified specific events and parent behaviors that strain the couples' relationship during the childhood cancer trajectory. This information can inform the development of a couple's intervention. Prospective research is needed to better understand how childhood cancer affects caregivers' partnerships through survivorship and beyond.