BACKGROUND A lipoma is a benign tumor made of fat tissue. Diaphragmatic lipomas are frequently reported in case studies. CASE REPORT This study presents a case of diaphragmatic lipoma in a woman with rheumatoid arthritis who was complaining of shortness of breath. A literature review of previously reported diaphragmatic lipoma cases was also carried out. In our patient, normal vital signs were detected, and laboratory results showed that antinuclear antibody, complete blood count, erythrocyte sedimentation rate, and C-reactive protein levels were high. A high-resolution CT scan showed pulmonary nodules and an incidentally found diaphragmatic lipoma. The patient was prescribed corticosteroids, methotrexate, folic acid, and chloroquine. The 3-month follow-up visit revealed symptomatic improvements in breathing difficulties and joint attacks. CONCLUSIONS Diaphragmatic lipoma should be identified to avoid misdiagnosis. Most cases of lipoma require observation. Surgical treatment is indicated only if the mass is symptomatic, increasing in size, or of uncertain nature.