To report a case of Behcet's disease presented with bilateral hypopyon after sequential cataract surgery masquerading delayed onset post-operative endophthalmitis.A 53-year-old man with a history of sequential uneventful cataract surgeries came to our clinic with decreased vision (0.3 LogMAR) since 2 days ago and bilateral hypopyon in his both eyes. The primary diagnosis was chronic late-onset endophthalmitis.There was no lid edema or chemosis on the external examination. On slit-lamp examination, the cornea was clear, the pupil was well reactive with no posterior synechia, the intraocular lens was centered with good red reflex, however, bilateral hypopyon was detected in his both eyes which was more prominent in the left eye. The eyes were fairly calm and absence of vitreous reaction on slit-lamp examination, there was no pain and photophobia. Further, on physical examination, oral mucosal ulcerations were detected. His systemic workup revealed Behcet's disease with HLA-B5 positive serology.In cases with delayed onset hypopyon following cataract surgery, inflammatory diseases such as Behcet's disease should be considered. Appropriate history taking and physical examinations in the context of serologic laboratory investigations may lead to the proper diagnosis.