Sarcoidosis is a generalized systemic chronic inflammation that rarely involves the orbit. As a chronic inflammation, sarcoidosis typically manifests with an insidious onset and slowly progressive course. We report a case of acute-onset proptosis resulting from a rapidly growing diffuse orbital mass that simulated malignant growth, which was biopsy proven to be the first manifestation of systemic sarcoidosis. The patient demonstrated complete resolution of proptosis and systemic involvement with long-term corticosteroid treatment.