The study focuses on individuals aged 0-20 when they were exposed to radiation as a result of two radiation accidents related to the release of radioactive waste to the Techa River and the formation of the East Urals Radioactive Trace in the Southern Ural. These people were integrated in the Urals Childhood Exposure Cohort (UChEC). The objective of the paper is to analyze breast cancer incidence rates in the Urals Childhood Exposure Cohort on the basis of updated data and with the use of the improved dosimetry system. Breast cancer incidence rates in females from the UChEC (established in 2019) have been analyzed for the first time. The female subcohort includes 15,853 individuals. Over a 63-year follow-up period (from 1956 to 2018), 199 cases of breast cancer were recoded and 434,408 person-years at risk were registered in the follow-up area. Standard statistical methods for parameter calculation per 100,000 persons with 95% confidence intervals were used to assess baseline incidence rates. A multivariate analysis was conducted using a simple parametric excess relative risk model by the method of Poisson regression and confidence interval calculation by the maximum likelihood method to evaluate baseline rates and radiogenic risk. The mean dose accumulated in the mammary gland over the follow-up period in women of the entire cohort was 34 mGy, the maximum dose was 1 Gy. The determined patterns of breast cancer incidence were found to be in agreement with the global trends, i.e. an increase in baseline rates over time, with age; high levels of breast cancer incidence in women who gave birth less than twice as compared to those who gave birth 2 and more times; higher levels of breast cancer incidence in people who have first-degree relatives with breast cancer or prostate cancer. The analysis of dose dependence of breast cancer incidence in women revealed an increased risk with increasing dose in women with genetic predisposition as well as in those who did not give birth or gave birth less than twice. Individuals exposed to radiation under the age of 10 have a statistically significant increase in the risk for breast cancer development with increasing dose.