Despite the growing population of young cancer survivors of reproductive age, the risk of cancer in offspring born to female cancer survivors has yielded inconsistent results. Therefore, this study aimed to investigate the risk of cancer among the offspring of female cancer survivors by maternal age at delivery, maternal age at cancer diagnosis, maternal cancer type, and the time interval between cancer diagnosis and pregnancy. Using nationwide retrospective mother-child linked data from the Korean National Health Insurance Service, we included the first child (N = 8031) of female cancer survivors aged <
40 years after excluding thyroid cancer survivors and matched controls (N = 24,093) between 2005 and 2019. Subgroup analysis was performed according to maternal age at delivery, maternal age at cancer diagnosis, maternal cancer type, and the interval between cancer diagnosis and delivery. Among the offspring, 19 children of cancer survivors and 30 in the control group were diagnosed with cancer, with a mean age of 2.0 years at diagnosis. The most prevalent cancer type was leukemia (26.5%), followed by liver tumor (10.2%) and brain tumor (8.2%). The hazard ratio (HR) for cancer in the offspring of female cancer survivors was 1.91 (95% confidence interval (CI) = 1.07-3.38) demonstrating consistently high risk over the follow-up period. HRs for cancer risk in offspring were high across all subgroups despite the low statistical power. Our study indicated that offspring born to maternal cancer survivors had an increased risk of cancer.