In a search for new drug-like molecules, we investigated Haplophyllum tuberculatum as a potential source of a-glucosidase inhibitors. Five new natural products (1-5), and one previously synthesized compound (6), isolated here as a natural product for the first time, were isolated from an ethyl acetate extract. Additionally, fifteen known compounds (7-21) were also characterized. The structures of all compounds were elucidated by 1D- and 2D-NMR techniques and HR-ESI-MS. All phytochemicals were evaluated for inhibitory activity against a-glucosidase enzyme. Among them, six compounds exhibited notable inhbition with IC50 values of 2.28 ± 0.64 to 8.94 ± 0.37 uM, seven compounds had appreciable activity with IC50 values ranging from 12.14 ± 0.35 to 24.60 ± 0.57 uM, whilst six compounds exhibited weak activities with IC50 values of 36.52 ± 1.68 and 260.53 ± 3.18 uM, respectively, compared to the standard drug acarbose (IC50 = 875.75 ± 1.24 uM). The a-glucosidase inhibitory activities of all compounds are reported here for the first time. A kinetic study of the most potent compounds was also performed and exhibited concentration dependent type of inhibition. Furthermore, a structure- based prediction of the compounds’ binding mode suggested that these inhibitors fitted exceptionally well within the active site of the target enzyme, a-glucosidase, forming multiple hydrogen and hydrophobic interactions with its active site residues. In conclusion, compounds with potent a-glucosidase inhibitory activity are abundant in nature and can be explored and further developed for treating diabetes mellitus.