A 28-year-old female patient presenting with complaints of shortness of breath was diagnosed with diffuse pulmonary lymphangiomatosis based on radiological examinations and pathological analyses. This rare disease is characterized by the abnormal proliferation and dilation of lymphatic vessels. Although it is typically observed at younger ages in the literature, it can also be rarely diagnosed in adults. Our case emphasizes the importance of differential diagnosis for diffuse pulmonary lymphangiomatosis. The clinical, radiological, and pathological findings of the disease are discussed in detail.