Cancer is among the deadliest diseases in the world, especially in developed countries where modern treatments are not available to everyone. In North Africa, and especially in Algeria, few herbal treatments against cancer have been documented despite the richness of flora in these countries. This research aim to documents the medicinal plants used by patient to fight cancer in the northwest of Algeria. Data were collected through ethnobotanical surveys engaging 211 cancer patients in hospitals (departments of medical oncology) in two of the largest provinces in northwest Algeria (Tiaret and Tlemcen). The data were organized into usage reports (UR), while the Informant Consensus Factor (ICF) was calculated to evaluate agreement among informants. The patients investigated were mainly women, of middle age (41-50 years) and illiterate. In total, 53 medicinal plants used against several types of cancer have been identified. These plants are dominated by Lamiaceae, Apiaceae and Rosaceae. The leaves and powder of plants are most often used in traditional preparations often mixed with honey. The plants most often cited in the survey were Aristolochia longa, Aquilaria malaccensis, Ephedra alata subsp. alenda, while the most often treated cancer were breast, cervical, colorectal and stomach. 23 plants are not known as a treatment against cancers in North Africa, while 25 plants already known as treatment for cancer were cited here to treat specific new types of this disease.