Background: With the problems of increasing levels of drug resistance and difficulties to afford and access effective antimalarial drugs in poor and remote areas, herbal medicines could be an important and sustainable source of treatment. Argemone mexicana L. (AM) is a medicinal plant known long ago in several countries for treatment of numerous diseases including malaria. The aim of this study was to conduct a survey on the use of AM in the prevention and treatment of uncomplicated malaria in selected districts of Jimma Zone, Oromia Regional state, Ethiopia. Methods: A community-based cross-sectional study was conducted in two selected districts in Jimma Zone, southwest Ethiopia. In total, 552 participants from 17 kebeles (villages/communities) and 18 traditional healers of the districts were interviewed. Data collection was conducted from April 27 to May 18, 2020 using pre-tested structured questionnaires. The data were analyzed using Epi Info 7.0 and the descriptive statistics were used to summarize the results. Results: The study indicated that AM is available, known by 39.8% of the respondents and used for prevention and treatment of malaria by 5.7% of the population. All traditional healers interviewed knew the plant, and 44.4% use it for treatment of malaria. In addition, AM is especially used to treat malaria, amoebiasis, diarrhea, cough, and tuberculosis. Conclusion: The availability and use of AM to treat malaria was verified in both community and traditional healers. AM, which was found effective as antimalarial plant in high Plasmodium falciparum endemicity in Mali, is also well known and accepted in these areas of Ethiopia for the treatment of malaria. Further research is needed to assess wether AM is also effective against malaria in Ethiopia where P. vivax and P. falciparum coexist.