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.