A decoction of the roots (31.6-316 mg/kg) from Stevia serrata Cav. (Asteraceae) as well as the main component (5-150 mg/kg) showed hypoglycemic and antihyperglycemic effects in mice. The fractionation of the active extract led to the isolation of dammaradiene acetate (1), stevisalioside A (2), and three new chemical entities characterized by spectroscopic methods and named stevisaliosides B-D (3-5). Glycoside 2 (5 and 50 mg/kg) decreased blood glucose levels and the postprandial peak during oral glucose and insulin tolerance tests in STZ-hyperglycemic mice. Compounds 1-5 were tested also against PTP1B1-400 and showed IC50 values of 1180.9 ± 0.33, 526.8 ± 0.02, 532.1 ± 0.03, 928.2 ± 0.39, and 31.8 ± 1.09 μM, respectively. Compound 5 showed an IC50 value comparable to that of ursolic acid (IC50 = 30.7 ± 0.00 μM). Docking studies revealed that 2-5 and their aglycones bind to PTP1B1-400 in a pocket formed by the C-terminal region. The volatilome of S. serrata was characterized by a high content of (E)-longipinene, spathulenol, guaiadiene, seychellene, and aromandendrene. Finally, a UHPLC-UV method was developed and validated to quantify the content of 2 in the decoction of the plant.