Background & Aim: Medicinal plants can be a good replacement for common cancer treatment including chemotherapy, radiation therapy and surgery because they don’t have many side effects. The aim of this study was to investigate the effect of temperature on the free radical scavenging in the presence of medicinal plants.Experimental: For determination of free radical scavenging activity was used the stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay at different temperatures. Ethanolic extracts of Sage (Salvia officinalis), red cabbage (Brassica oleracea), walnut (Juglans regia L.), yellow sweet clover (Melilotus officinalis) and hawthorn (Crataegus oxyacantha) one by one and then the mixtures of each pair of plants were investigated.Results: The most free radical scavenging percentages are related to plants in single forms not mixtures. The results demonstrated that with increasing temperature, free radical scavenging increased in the presence of sage, while it decreased in the presence of hawthorn. The highest free radical scavenging percentages at temperatures ranging from ambient to body and fever are related to sage at 25˚C, and then walnut leaves at 37˚C and finally, hawthorn at 40˚C.Recommended applications/industries: The results indicated that for preventing herb-herb interactions, medicinal plants as tea, food and fruit are used alone. Manuscript profile