Pulmonary lymphangitic carcinomatosis (PLC) is a type of lymphangitic spread of cancer cells, from a primary site to the pulmonary vasculature and lymphatics. Corticosteroids are recommended for PLC by clinical guidelines, although scientific evidence for this traditional practice is still lacking. We report a patient with lung cancer who developed clinically diagnosed PLC and was successfully treated with steroid treatment. The pulmonary shadows suggestive of PLC were remarkably improved, as well as her symptom. Corticosteroids are worth trying when PLC is clinically suspected.