Background: The purpose of this study was to analyze the effect of breast cancer therapy on fertility concerns and sexuality of young mothers with breast cancer in Germany. Methods: During a mother-child rehabilitation program, 1,191 young mothers with locoregional primary breast cancer, treated between 2006 and 2014, were recruited. Data included sociodemographic data, TNM stage, tumor biology, therapies, and patient-reported outcomes such as sexuality and fertility concerns. Results: The mean age at diagnosis was 40 years. Approximately a quarter of the patients stated that family planning had not been completed at the time of diagnosis. Nearly half of all patients had been informed as to how treatment could affect fertility, but counseling at a specialized fertility center was offered to only 13%. Of all patients, 4% took a consultation and 2% underwent fertility preservation procedures. Conclusion: Our study indicates that only a minority of patients is referred to fertility centers although family planning is incomplete at the time of diagnosis in about 25% of young women with breast cancer. Thus, these patients should not only be informed about the effects of treatment on fertility and sexuality, but should be referred to a fertility center.