Meeting the needs of an ageing population, particularly in the global South, is increasingly an issue for WASH service provision. An ageing-related issue for women, warranting specific attention from the WASH sector, is the perimenopause, but this is often not discussed publicly. Drawing on data from the UK and Ghana, this paper provides recommendations for meeting the additional WASH needs of women as they experience the perimenopause (the transition period to menopause). Finding these ‘hidden’ needs involved a UK-based phenomenological review and mixed feminist methods in two low-income urban communities in Accra and Kumasi, Ghana. The hidden WASH needs of perimenopausal women included understanding the perimenopause, menstrual hygiene management, urine incontinence management, bathing, and laundry. Community awareness, engagement and empowerment, and ensuring good perimenopausal health can begin to address these needs. Infrastructural measures for perimenopausal women include a continuous water supply, user-friendly bathing and laundry infrastructure, and gender-sensitive, accessible toilets with discrete sanitary disposal bins. High-absorbency sanitary products are important for managing heavy menstruation. A better understanding of the needs of perimenopausal women and training on how to meet these would benefit the WASH sector in ensuring that perimenopausal women are not left behind in efforts to meet the Sustainable Development Goals.