In this study, 18 novel thiochroman-4-one derivatives incorporating oxime ether and 1,3,4-oxadiazole thioether moieties were synthesized and their structures analyzed by 1H NMR, 13C NMR, and HRMS. Their in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) as well as antifungal activities against Botrytis cinerea (B. cinerea), Verticillium dahliae (V. dahliae), and Fusarium oxysporum (F. oxysporum) were determined. Bioassay results showed that compound 6-chloro-2-(5-(methylthio)-1,3,4-oxadiazol-2-yl)thiochroman-4-one O-methyl oxime (7a) was...