In urban Comoros, a substantial portion of healthcare is delivered through informal channels, including unregulated medicine vendors and traditional healers. Understanding this sector is crucial for public health policy and for ensuring safe maternal and gynaecological care. This systematic review synthesises evidence on informal healthcare provision and medicinal access in urban Comoros. It aims to map the types of informal providers, analyse the factors driving their use, and assess documented impacts on health outcomes, with a focus on obstetrics and gynaecology. A systematic search of multiple academic databases and grey literature sources was conducted following PRISMA guidelines. Studies published in English and French were included. Screening, data extraction, and quality assessment were performed independently by two reviewers, with discrepancies resolved through consensus. The findings indicate a heavy reliance on the informal sector, which is frequently the first point of contact for urban residents. A dominant theme was the procurement of medicines, including antibiotics and analgesics, from informal pharmacies and street vendors without prescription, driven by affordability, accessibility, and convenience. Documented evidence on specific health outcomes was limited. Informal healthcare is a pervasive and embedded component of the urban health system in Comoros. It addresses critical gaps in formal care but raises significant concerns regarding medication safety, appropriate use, and the overall quality and regulation of care. Future research should employ robust methodologies to quantify health outcomes linked to informal sector use. Policy should focus on engaging and regulating informal providers, rather than solely suppressing them, while concurrently strengthening the formal public health system to improve equitable access to quality medicines and care. informal healthcare, medicinal access, urban health, Comoros, systematic review, maternal health, gynaecology This review consolidates the fragmented evidence on a critical yet under-studied component of Comoros' health system, providing a foundation for future research and informed policy dialogue aimed at integrating and regulating informal healthcare provision.