The aim of this study was to determine the effects of Allium tuncelianum ethanol extract on nine important plant pathogens and the amount of total phenolic compounds in tomato and pepper. Three extract doses (0.5%, 1%, and 1.5%) were applied in the form of irrigation water against soil-borne pathogens while the spraying method was applied for the bacterial speck disease in tomato and disease severity was determined. According to the pot trial results, higher doses of extract reduced the disease severity of Botrytis cinerea, Fusarium oxysporum f.sp. lycopersici, Pythium deliense, Rhizoctonia solani and Sclerotium rolfsii and the 1.5% dose reduced disease severity by 76.8%, 56.6%, 41.4%, 85.8%, and 53.1%), respectively. Total phenolic compounds were determined spectrophotometrically. The extract applications have increased the amount of phenolic compounds in a certain level compared to the control in tomato. However, it was also observed that this level was much higher when the different doses of extract and pathogen combinations were applied. Conclusively, ethanol extract of the garlic used in our study reduced the development of some important pathogens, and promising results were obtained.