The purpose of this review is to summarize the available antidiabetic medicinal plants in the Kingdom of Saudi Arabia with its phytoconstituents and toxicological findings supporting by the latest literature. Required data about medicinal plants having antidiabetic activities and growing in the Kingdom of Saudi Arabia were searched/collected from the online databases including Wiley, Google, PubMed, Google Scholar, ScienceDirect, and Scopus. Keywords used in search are in vivo antidiabetic activities, flora of Saudi Arabia, active ingredients, toxicological evaluations, and medicinal plants. A total of 50 plant species belonging to 27 families were found in the flora of Saudi Arabia. Dominant family was found Lamiaceae with 5 species (highest) followed by Moraceae with 4 species. β-Amyrin, β-sitosterol, stigmasterol, oleanolic acid, ursolic acid, rutin, chlorogenic acid, quercetin, and kaempferol are the very common bioactive constituents of these selected plant species. This paper has presented a list of antidiabetic plants used in the treatment of diabetes mellitus. Bioactive antidiabetic phytoconstituents which showed that these plants have hypoglycemic effects and highly recommended for further pharmacological purposes and to isolate/identify antidiabetes mellitus (anti-DM) active agents also need to investigate the side effects of active ingredients.