Objective To explore the potential association between IgD-type multiple myeloma (MM) and a previous history of breast cancer (BC). Methods A retrospective analysis was conducted on the clinical and pathological data of a patient with breast can⁃ cer combined with IgD-type MM，who was admitted to a tertiary hospital in Shaanxi Province in February 2022. Relevant literature was also reviewed. Results The patient was a 78-year-old female diagnosed as breast malignancy (right，PT1N0M0，stage I) 12 years ago at our hospital. She underwent modified radical surgery for right breast cancer，and was given four courses of chemotherapy with TC regi⁃ men (docetaxel，toltestrone) after surgery. After more than 11 years after treatment，the patient was diagnosed with IgD-type MM based on bone marrow aspiration and immunofixation electrophoresis in February 2022. She had received VRD regimen (bortezomib，lenalido⁃ mide，dexamethasone) for four courses of induction chemotherapy to achieve complete remission. Induction chemotherapy with the VRD regimen (bortezomib，lenalidomide，dexamethasone) was administered for four cycles，achieving complete remission. Due to intolerance to lenalidomide，maintenance treatment was switched to the VD regimen (bortezomib，dexamethasone). The patient is currently on regu⁃ lar follow-up visits with stable disease，and the bone marrow examination indicates complete remission of MM. Conclusion The com⁃ bination of breast cancer and IgD MM is rare，and further research is required to elucidate the relationship between these two condi⁃ tions. This case provided a new research direction for studying malignant tumors combined with MM.