Non-traumatic subperiosteal orbital hematoma is a rare finding and uncommon cause of proptosis. Reported cases describe an association with increased venous pressure. However, it is important to note that there is also an association with sinusitis, which must be differentiated from subperiosteal abscess. This article describes the unique imaging features of subperiosteal hematoma in the setting of sinusitis, as well as the suspected pathophysiology.