The idiopathic orbital inflammatory syndrome (pseudotumor orbita) is an unexplained disease that mimicsthecomplications of acute rhinosinusitis. Intense polymorphic lymphoid infiltration develops with inflammation. Themasses in the orbita can be seen by 5% to 8%. It can cause nonspecific orbital symptoms, such as proptosis andswelling on eyelids. In our case, the patients presented to the eye outpatient clinic with swelling complaint andacute atopic conjunctivitis treatment was initiated but the patients who did not regression complaints were submitted.The patient’s magnetic resonance imaging (MRI) showed bilateral lateral rectus muscle thickening. Idiopathicorbital inflammatory syndrome (pseudotumor orbita) responded to the steroid treatment. Idiopathic orbitalinflammatory syndrome (pseudotumor orbita) is benign, but can be confusedwith sinusitis complications withhigh morbidity and mortality.