Ferula persica, Paronychia argentea, and Pistacia atlantica are three of the plants widely recommended by the herbalists and used for their hypoglycemic activity in Jordan. Aqueous extracts of these plants were tested in vitro for their alpha amylase inhibitory activity and in vivo for their hypoglycemic activity in normoglycemic and streptozocin-induced hyperglycemic rats. Although the three plants were advocated for their hypoglycemic effects in Jordanian traditional herbal medicine; none of them showed significant hypoglycemic activity compared to the untreated animals. Paronychia argentea and Pistacia atlantica showed significant alpha amylase inhibitory activity while Ferula persica did not demonstrate any alpha amylase inhibitory activity. The main conclusion of this work was the concern over the unjustified claims of the uses of some herbal medicine in Jordan and possibly in other countries.