According to relevant literature, the consumption of seahorses has been used to increase male functions by improving blood flow and decreasing blood pressure. Thus, it was theorized that seahorses may also be effective against hypertension. Herein, vasodilation caused via the inhibitory effect of angiotensin-converting enzymes (ACEs) in peptides was elucidated by studying the seahorses (Hippocampus abdominalis) farmed M Jeju in South Korea. Hydrolysate was prepared using the Protamex (SHP) enzyme. The ultrafiltration system was adopted to separate certain fractions from SHP according to different molecular weights (SHP-I, MW > 10 kDa; SHP-II, MW = 5 -10 kDa; SHP-III, MW < 5 kDa). The fraction with the lowest molecular weight (SHP-III) and with a low IC50 value (0.044 +/- 0.005) for the ACE inhibitory effect was further separated by Sephadex G-10. Three ACE inhibitory peptides from SHP-III were isolated and identified using the Q-TOF mass spectrometer (Ala-Pro-Thr-Leu, Cys-Asn-Val-Pro-Leu-Ser-Pro, and Pro-Trp-Thr-Pro-Leu). Furthermore, SHP-III-induced systolic blood pressure varied with the concentrations, as observed in the spontaneously hypertensive rat (SHR). SHP and the isolated peptides were observed to show vasodilation via ACE inhibitions and resulted in lowering the blood pressure of the SHR. These results imply that peptides from seahorses can augment male functions.