Pregnancy-associated breast cancer is a rare disease with an incidence of 1:3000. There is no indication anymore to terminate the pregnancy since the maternal prognosis will not be influenced. Due to physiologic pregnancy-related changes in the breast, the interpretation of clinical findings, breast ultrasound and mammography is more demanding. There is often a diagnostic delay in detecting pregnancy-associated breast cancer. Mastectomy and axillary lymphonodectomy compose the surgical therapy. In the third trimester, breast conserving surgery and radiotherapy postpartum is an option. Chemotherapy can be administered relatively safe in the second and third trimester. Radiotherapy, hormonal therapy and trastuzumab are contraindicated during pregnancy. Patients with pregnancy-associated breast cancer should be seen and treated in an interdisciplinary setting, preferably in a specialized centre.