In the first two parts of this series of review articles, we presented the anticancer and anti-inflammatory activities of the most important wild edible plants of eastern Mediterranean region, which we named as the “Deca-plants” (D-P). In this review article, we will present the antidiabetic activities of these very important plants. Comparing with anticancer and anti-inflammatory activities, the overall antidiabetic activity of the D-P is moderate, but there are clear differences between the ten species. Based on this fact and on the knowledge that the D-P contain several natural products with proven antidiabetic activity, in the discussion section (4), possible future research directions will be indicated. In addition to presenting the reported antidiabetic activity of the plants, some important statistical facts about diabetes will be presented, as well as ethnomedicinal use of these plants for diabetes treatment, in the reviewed region. For the purpose of comparison and comprehensiveness, in the last part of this article, four Non-Deca-Plants with reported antidiabetic activity will be shortly reviewed, when the criteria of selection are wild and edible.