1-deoxynojirimycin (DNJ) is a well-known α-glucosidase inhibitor. A series of phenyltriazole-deoxynojirimycin hybrids containing C₄ and C₆ (4 and 6 methylenes, respectively) linkers were synthesized. These novel compounds were assessed for preliminary glucosidase inhibition and cytotoxicity tests in vitro. Among them, compounds 12–14 and 16–20 (IC₅₀: 105 ± 9–11 ± 1 μM) were more active than deoxynojirimycin (DNJ, IC₅₀ = 155 ± 15 μM). The kinetics of enzyme inhibition measured by using Lineweaver–Burk plots indicated that compounds 18 and 19 were competitive inhibitors. In addition, a molecular docking study of α-glucosidase revealed that the interaction modes and the orientations of compound 18 and DNJ were clearly different. Furthermore, in tissue culture, HL60 cell compounds showed no cytotoxicity at low concentrations. When the concentration reached 50 µM, only compound 20 exhibited cytotoxicity. The structure–activity relationships exhibit that the length of the linker and the nature of 4-position substituents on the phenyl have a significant effect on the inhibitory potency of glucosidases and cytotoxicity.