This is a case of an 11-year-old male with an ethmoid sinus mucocele who presented to our emergency department with an orbital mass. This mucocele was most likely related to an ipsilateral orbital subperiosteal abscess that required endoscopic drainage 9years ago. Mucoceles are mucus-filled, epithelial-lined sacs that slowly develop in the paranasal sinuses when sinus drainage is obstructed by inflammatory processes, trauma, or prior surgery. They are rare in children and should be suspected in patients with progressive headache or orbital complaints.