Primary vaginal cancer is a rare cancer and clinical evidence to support recommendations on its optimal management is insufficient. Because primary vaginal cancer resembles cervical cancer in many aspects, treatment strategies are mainly adopted from evidence in locally advanced cervical cancer. To date, the organ-sparing treatment of choice is definitive radiotherapy, consisting of external beam radiotherapy and brachytherapy, combined with concurrent chemotherapy. Brachytherapy is an important component of the treatment and its steep dose gradient enables the delivery of high doses of radiation to the primary tumour, while simultaneously sparing the surrounding organs at risk. The introduction of volumetric CT or MRI image-guided adaptive brachytherapy in cervical cancer has led to better pelvic control and survival, with decreased morbidity, than brachytherapy based on x-ray radiographs. MRI-based image-guided adaptive brachytherapy with superior soft-tissue contrast has also been adopted sporadically for primary vaginal cancer. This therapy has had promising results and is considered to be the state-of-the-art treatment for primary vaginal cancer in standard practice.