Most of the plant species are susceptible to various ecological constraints, including high temperature stress. Endophytic fungi can defend the host crops from the extreme effects of thermal stress. We isolated fungal endophytes from a wild plant species Sonchus asper L. to study its effect on the physicochemical characteristics of Helianthus annuus L. and Glycine max L. exposed to high temperature stress. Biochemical and physiological parameters, such as chlorophyll contents, total biomass and height of the Helianthus annuus and Glycine max were promoted, whereas the production of ROS (Reactive Oxygen Species) and lipid peroxidation were inhibited in the fungal inoculated plants. Furthermore, higher amounts of ROS-degrading antioxidants [CAT (catalase), SOD (superoxide dismutase), POD (peroxidase), GR (glutathione-reductase) and AAO (ascorbic acid oxidase)], sugars, proteins, lipids and phenolics were noted in host crops. Lower concentration of proline and ABA on the other hand was observed in plants inoculated with fungal strain and exposed to heat stress. The potent strain was found to be Stemphylium solani after amplification of the ITS region of 18 S rDNA. The results concluded that S. solani can be handy in mitigating heat stress in food crops.