Leaf spot and blight symp toms caused by Al ternaria al ter nata have been widely oc curred on toma toes and pota toes in Egypt. In at tempts to im prove the sus tain abil ity of crop pro tec tion, the use of nan otech nol ogy in pro duc ing nano - fungicides as an eco - friendly con ve nient ap proach was needed to con trol such dis eases. Ti ta - nium diox ide nanopar ti cles (TiO 2 NPs) and Sil ver nanopar ti cles (Ag NPs) were biosyn the sized by As pergillus ver - si color KY509550 through sur face res o nance peaks at 340 and 400 nm, re spec tively. The prepa ra tion of Se le - nium nanopar ti cles (SeNPs) was done us ing glu cose so lu tion method at 387 nm. The sizes of the pre pared nanopar ti cles were 47.15, 36 and 78 nm for TiO 2 NPs, Ag NPs and SeNPs, re spec tively. It was de tected from Trans mis sion Elec tron Mi cro scope (TEM) analy sis that TiO 2 NPs and Ag NPs were well dis persed in the so lu tion with out any ag glom er a tion com pared with SeNPs. The an ti fun gal ac tiv ity of TiO 2 NPs, Ag NPs and SeNPs at three con cen tra tions viz.50, 75 and 100 ppm were es ti mated against A. al ter nata by lab o ra tory tri als. The biosyn the sized TiO 2 NPs ex hib ited the high est in hibitory ef fect at100 ppm against A. al ter nata and in turn re - sulted in 90% de crease of its mycelial growth in vitro tri als. The green house and field tri als ex plored also that TiO 2 NPs was sig nif i cantly ef fec tive in re duc ing dis ease sever ity (DS) as shown by the cal cu lated area un der dis ease pro gres sive curve (AU DPC). SeNPs re vealed close re sults to that ob tained by TiO 2 NPs for both tri als. Ag NPs showed a mod er ate ef fect at the tested con cen tra tions in all tri als. Nanopar ti cles could be pow er ful and eco - friendly nano - fungicides for bi o log i cal con trol of tomato leaf blight.