Background: Previous studies have described suicidal ideation among survivors of childhood cancer, but small numbers of events limit the understanding of suicide risk. The objectives of this study were to assess whether childhood cancer survivors are at increased risk of suicide in comparison with the general population and to determine risk factors associated with risk in a population-based cohort. Methods: First primary malignancies among individuals aged 0 to 19 years from 1975 to 2016 were identified from Surveillance, Epidemiology, and End Results (SEER) databases. Standardized mortality ratios (SMRs) of suicide were obtained via SEER*Stat software from SEER 9. Fine and Gray proportional hazards models were used to identify suicide-associated factors among childhood cancer patients included in SEER 18. Results: In all, 96,948 childhood cancer cases and 89 suicides were identified. Across all attained ages, the suicide risk for individuals with a childhood cancer history (11.64 per 100,000 person-years) was similar to the risk for those without a cancer history (SMR, 1.14; 95% confidence interval [CI], 0.91-1.43). However, for survivors alive beyond the age of 28 years (the median age of death by suicide), the suicide risk was significantly elevated (suicides per 100,000 person-years, 22.43; SMR, 1.40; 95% CI, 1.02-1.87). Females (hazard ratio, 0.29; 95% CI, 0.18-0.59; P <.01) had lower risks than males. Conclusions: These results suggest that long-term childhood cancer survivors may be at increased suicide risk. Male sex is an independent risk factor for suicide. However, the absolute risk of suicide in older survivors is still low at ~1 per 5000 person-years. Future efforts should identify survivorship strategies to mitigate suicide risk.