Although malignancies during pregnancy are relatively rare, breast cancer is the most common neoplasm affecting pregnant women. Diagnostic workup and multimodal treatment of breast cancer during pregnancy must be weighed against the potential risk to the fetus. With the increasing number of breast cancer diagnoses during pregnancy, this narrative review aimed to outline the epidemiological and molecular background, followed by presenting available therapeutic options. Surgery remains the treatment of choice among patients with breast cancer during pregnancy. However, systemic therapy based on anthracyclines, fluoropyrimidines, taxanes, and platinum derivatives is possible after 12 weeks of gestation and can be administered in both neoadjuvant and adjuvant settings. Hormone therapy should not be used during pregnancy as it may affect the fetus. Studies suggest that estrogen or progestogen therapy during pregnancy may cause malformations in children exposed in utero. One known phenomenon is the congenital fetal defect Goldenhar syndrome (manifested by hemifacial hypoplasia and genital malformations). There are no absolute contraindications for radiotherapy in pregnant patients. The potential benefits and risks of radiotherapy, including the potential risk to the fetus, should be carefully considered. Although it is recommended that radiation be delayed until after delivery, the critical threshold for teratogenic effects has been set at 0.1 Gy. The dose can be further reduced by using additional shielding in the pelvic region. Importantly, the sensitivity of fetal tissues to radiation and the risk of radiation-induced toxicity depend on gestational age. Novel diagnostic and therapeutic directions are being investigated. Due to its complexity, the treatment process should be managed by a multidisciplinary team, in which the presence of an oncologist, surgical oncologist, obstetrician, and neonatologist is essential.