Background Parents of children with cancer are susceptible to psychological distress; however, many parents also report posttraumatic growth (PTG). The objective of this study was to explore the variables associated with PTG in parents of children with cancer who were either on treatment or off treatment. Methods One hundred and nineteen parents (71 mothers and 48 fathers) of children with cancer completed self‐report questionnaires, including the PTG Inventory, Center for Epidemiologic Studies Depression Scale, State‐Trait Anxiety Inventory, and Impact of Event Scale‐Revised. Demographic data and children's medical information were also collected. Multivariate linear regression analyses were conducted to investigate the variables associated with PTG. Results The mean age of participants was 41.4 years (SD = 6). Higher PTG Inventory scores were associated with parents' lower trait anxiety (P = .028), parents' sex (female; P = .004), treatment status (within 12 months from treatment end compared with on‐treatment; P = .048), surgery (P = .007), and late effects (P = .01). Conclusions Parents' PTG was associated with children's clinical characteristics, parents' sex, and parents' anxiety levels. When dealing with PTG, the parents' psychological characteristics and children's clinical characteristics should be considered. Particularly for parents with high trait anxiety, it is important to reduce anxiety first before addressing PTG.