The aim of this paper is to review studies conducted on the topic of essential oils and isolated volatile compounds in the composition of essential oils which act as inhibitors of α-glucosidase enzymes, whose action may have a negative effect in patients with type II diabetes mellitus. The subject of the study were terpene rich essential oils as well as isolated terpenoid compounds. To this end, available books and online databases (Web of Science, PubMed, PubChem, PMC, Science Direct and RCSB Protein Data Bank) have been reviewed. α-Glucosidases have the role of hydrolyzing complex carbohydrates in the small intestine, thereby releasing α-glucose which is then absorbed into the blood. Synthetic enzyme inhibitors are used as drugs, but because of the frequent side effects of long-term use, scientists are looking for new inhibitors, isolated from natural sources, such as plants. The results showed that the essential oils of the plants Curcuma longa L., Rhaponticum acaule (L.) DC., Hymenocrater bituminosus Fisch., Aegle marmelos (L.) Corrêa, Thymus spathulifolius Hausskn. and Velen and Centaurium erythrea Rafn had significant inhibitory activity on the enzyme α-glucosidase. Very few isolated compounds have been tested for inhibition of this enzyme. Of those tested, ar-turmerone, (R)-(+)-limonene, (S)-(-)-perillyl alcohol and α-terpineol showed the best inhibitory activity