Primary vaginal cancer is not common, representing 1-2% of all female genital malignancies. We present a case of a third-degree uterine prolapse complicated by an isolated primary vaginal cancer and its surgical treatment. The cervix was clinically normal, but on the nearby prolapsed vaginal wall, a large exogenous hard lesion had developed. A biopsy of the lesion revealed a squamous carcinoma. The patient was asymptomatic and had no recurrence during the last 4 years of follow-up after surgical treatment with radiotherapy. The surgical treatment with or without radiotherapy is the optimum treatment for uterine prolapse with early-stage vaginal squamous cell carcinoma, although the majority of vaginal malignancies are treated with radiotherapy. We recommend always performing a biopsy prior to surgery in prolapse-induced ulceration.