Survivors of childhood, adolescent, and young adulthood malignancies have an increased risk of subsequent primary malignancies, particularly after exposure to therapeutic radiation. This study aims to evaluate the mode of surveillance and surveillance compliance, incidence and mode of detection of breast cancer, breast cancer phenotype, and outcomes after radiation-associated breast cancer (RBC) in a late-effects cohort. Women exposed to therapeutic radiation attending the late effects service from 1st January 2000 to 20th February 2013. All invasive and in-situ cancers, benign tumors, and deaths were evaluated. The incidence of breast cancer was compared to the Australian general population. Compliance with breast surveillance recommendations, clinicopathological features, and management of breast cancers were examined. The prevalence of RBC was 17.1%. Twenty-eight cases of RBC occurred in 24 women, out of 140 women exposed to chest radiation. Patients whose first attendance was ≥15 years after radiation exposure experienced the highest incidence of RBC at 23%. The incidence of breast cancer was 11.2 times the general population (P < .001). Compliance with surveillance mammography was observed in 18.4%. Breast cancers diagnosed after the first attendance to the service were more likely screen-detected (P = .002). Most were hormone receptor positive (84.0%), invasive ductal carcinomas (82.1%), and managed with mastectomy (89.3%). Patients attending a dedicated late effects service have a high burden of subsequent malignancies generally occurring after long latency. Judicious management with adherence to long-term surveillance guidelines is advocated. © 2020 John Wiley & Sons Australia, Ltd.