In this work, new 3,5-disubstituted-1,2,4-oxadiazoles were synthesized efficiently and evaluated for their inhibitory effects on human carbonic anhydrase (hCA) I and II. Most of them were more potent on hCAs than acetazolamide (AAZ). Compounds 10d and 17d were the most potent compounds on hCA I with IC50 values of 0.68 and 0.96 µM, respectively. Compounds 7d, 17d, 10d, and 3d were the most effective hCA II inhibitors with IC50 values of 0.40, 0.40, 0.65 and 0.71 µM. Molecular docking studies revealed that compounds 10d and 17d displayed π-π stacking interactions with Phe91 in the active site of hCA I. Compounds 10d and 17d were capable of forming π-π stacking interaction with His94 and π-cation interaction with Phe131 in the active site of hCA II. The alkylamino groups of both compounds contributed to crucial interactions in the active site of hCA II. Based on in silico data, all compounds were predicted to have good oral bioavailability and drug-likeness. Compounds 10d and 17d can be considered as promising inhibitors of both hCAs. All compounds were examined for their cytotoxicity towards human prostate (DU 145) and breast (MDA-MB-231) cancer cell lines compared to human embryonic kidney 293 cells (HEK-293). The tested compounds showed not only dose- and time-dependent but also cancer cell-specific cytotoxicity. Compounds 6d-11d were the most potent agents on DU 145 cells, whereas the most effective compounds on MDA-MB-231 cells were 6d, 15d-18d. The results suggest that compound 6d may serve as a hit compound for further mechanistic studies.