A series of 2,3-disubstituted 3H-quinazolin-4-ones was synthesized. Antimicrobial activities of the synthesized compounds were investigated against Gram (+ve) and Gram (-ve) bacteria, including B. subtilis, S. aureus, S. flexneri, P. aeruginosa, and S. typhi, and six fungi, namely Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, and Candida glabrata using the broth microdilution method. Compounds 9, 11, and 12 showed significant activities against the selected bacterial cultures, while 7-10, 12, 15, and 16 showed good to moderate antifungal activities. Compound 11 exhibited strongest leishmanicidal activity against Leishmania major (MHOM/PK/88/DESTO) promastigotes, while other compounds showed weak to moderate leishmanicidal activities.