The purpose of this register-based study was to identify factors related to disease, treatment, sociodemographics and comorbidity associated with taking early retirement among women treated for breast cancer, and to evaluate the risk for taking early retirement among breast cancer survivors who attended a six-day rehabilitation course. Material and methods. The study population consisted of 856 women who attended the rehabilitation course and a comparison group of 1 805 women who did not attend the course identified through the Danish Breast Cancer Cooperative Group. We obtained information on receipt of unemployment benefits, sickness benefits and early retirement pension for each of the years 19962007. Multivariate cox-regression models were used to analyze disease-specific, treatment-related, comorbidity and sociodemographics factors associated with early retirement after breast cancer and to evaluate the effect of attending a rehabilitation course on taking early retirement. Results. The rate of retirement was higher for women with somatic comorbidity (hazard ratio [HR], 1.91; 95% CI, 1.3; 2.9 for score 1, and HR 1.42; 95% CI, 0.7; 2.7 for score ≥2), previous depression (HR, 2.29; 95% CI, 1.7; 3.2) or having received sickness benefits in the year before their breast cancer diagnosis (HR, 3.75; 95% CI, 1.8; 7.8). Living with a partner was associated with a reduced hazard ratio for taking early retirement (HR, 0.70; 95% CI, 0.50.9). Having received chemotherapy, alone or in combination with anti-hormone treatment, reduced the hazard ratio (HR, 0.49; 95% CI, 0.3; 0.8 and HR, 0.5; 95% CI, 0.3; 0.8, respectively). The rate of retirement was higher for women the year after attending the rehabilitation course but returned to unity by three years. Discussion. The results of this study contribute to the identification of at-risk women and point to the need for tailored rehabilitation to avoid unnecessary marginalization of breast cancer survivors due to permanent labor market withdrawal.