Primary acquired melanosis (PAM) is an acquired pigmentation of the conjunctival epithelium, a preinvasive pigmented lesion. When it is associated with cellular atypia it can lead to the developement of melanoma. We report a case report of malignant melanoma of the conjuntiva, which arrised from the conjuntival PAM. The disease was too extensive for ocular conservation, therefore exenteration was performed. This case highlights the need for regular follow-up of patients with melanocytic lesions of the ocular adnexa, and particular attention to the surgical technique, and careful follow-up to detect further disease activity.