We report a case of occult spontaneous ocular perforation presenting as conjunctival chemosis in a patient with Marfan's syndrome (MFS). A 38-year-old female with MFS presented with bilateral conjunctival chemosis since 6 months. Best-corrected visual acuity was 20/20 in both eyes. On slit-lamp examination, a diffuse conjunctival chemosis was observed in both eyes without any signs of ocular hypotony (decreased visual acuity, low intraocular pressure, shallow anterior chamber, pupil distortion, hypotony maculopathy, and chorioretinal folds). Anterior-segment optical coherence tomography revealed a corneoscleral fistula at the left nasal limbus, without any similar finding in the right eye. A scleral patch was performed at the site of the perforation. At 3 month's follow-up, the left chemosis had regressed, with a stable best-corrected visual acuity in both eyes. However, on ultrasound biomicroscopy, another fistula at the right superior limbus was found, and the patient was referred for treatment with a scleral patch. In conclusion, conjunctival chemosis in a patient with MFS should raise the suspicion of an occult spontaneous ocular perforation.