Intraocular extension of a malignant melanoma of the conjunctiva is a rare entity. A 75-year-old woman underwent repeated surgery after receiving the diagnosis of a multilocular recurrent malignant melanoma arising from a primary acquired melanosis. Treatment included 2 lamellar sclerokeratectomies and percutaneous radiotherapy. Five years after initial surgery, intraocular extension of the melanoma was observed, and enucleation was performed. Findings from histopathological examination revealed a malignant melanoma occupying part of the ciliary body, the trabecular meshwork, and the iris. Eyes with recurrent malignant melanoma of the conjunctiva should be carefully monitored for intraocular extension. Deep excision of conjunctival melanoma, including lamellar sclerokeratectomy, may abolish the natural barrier against intraocular extension of malignant melanomas of the conjunctiva.