Primary breast lymphoma (PBL) represents 0.04–1% of all breast malignancies and is extremely rare in pregnancy. PBL affects women much more often than men and tends to be unilateral. Diffuse large B‑cell lymphoma (DLBCL) is the most common histological subtype of PBL. Treatment options include chemotherapy, radiotherapy, immunotherapy, and surgery, but are not clearly defined. We reported herein a case of bilateral primary breast lymphoma in a 35-year-old pregnant woman. After the diagnosis of DLBCL, R‑CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) was started in the second trimester. Postpartum intrathecal methotrexate prophylaxis and adjuvant radiotherapy were applied and a complete response was obtained. Twelve months after the initial diagnosis, our patient remains alive and relapse-free.