A 49-year-old man was urgently admitted due to edema in both leg and left toe pain. A chest radiograph revealed a solitary nodule in the right lung field. Detailed investigations including bronchoscopy and renal biopsy led to a simultaneous diagnosis of clinical stage IIIB pulmonary adenocarcinoma, minimal change nephrotic syndrome, antiphospholipid syndrome, and warm-type autoimmune hemolytic anemia. Prednisolone was administered for nephrotic syndrome, antiphospholipid syndrome and warm-type autoimmune hemolytic anemia, and 6 courses of chemotherapy with 70Gy radio-therapy were performed. The pulmonary nodule significantly decreased in size and the other three autoimmune diseases appeared to be well-controlled. Thirteen months after admission, multiple brain metastases developed along with worsening antiphospholipid syndrome symptoms including lupus anticoagulant. Following whole-brain irradiation, the brain metastases decreased in size and antiphospholipid syndrome symptoms improved. Thirty-nine months after the initial visit, the primary lung cancer, its brain metastasis and the 3 other autoimmune diseases appeared to be well-controlled. The temporal correlation of the lung cancer and the three autoimmune diseases suggests the latter may be paraneoplastic syndrome.