This article presents a case of fulminant interstitial lung disease (ILD) with macrophage activation syndrome (MAS) as a rare complication of adult-onset Still’s disease in a 43-year-old male patient. Initial presentation showed severe ILD. Early treatment focused on high-dose corticosteroids; however, disease remission could not be achieved. After an additional inflammatory focus and underlying malignancy were excluded, the triad of pancytopenia, fever, and high ferritin levels indicated MAS; bone marrow biopsy confirmed secondary hemophagocytic histiocytosis. Treatment with tocilizumab induced fast and effective therapeutic success.