We previously reported that the novel isoflavone-free peptide mixture (black soybean peptide, BSP) had several beneficial effects like antiobesity and hypotriglyceridemic effect. However, there are no reports for BSP on anti-hypertensive activity. BSP induced heme oxygenase-1 (HO-1) in HUVECs, thus investigated the HO-1-induced activity in HUVECs and the anti-hypertensive effects in SHR animal model. BSP significantly induced HO-1 expression both at transcriptional and protein levels in a time- and dose-dependent manner as measured by RT-PCR and Western blot analysis, respectively. These inductions were abolished by pretreatment of N-acetyl-cystein (NAC, 1~10 mM), but not by employing Tempol, a superoxide dismutase (SOD) mimetic (1~5 mM). As expected, enzymatic activity (~2 fold) determined by bilirubin formation assay and cGMP concentration (~6 fold) were significantly increased in BSP-treated cells. Based on the numerous evidences on the beneficial effects of HO-1 and our results, we investigated in vivo effects of BSP on the antihypertensive activity. The administration of BSP (1% in drinking water) significantly decreased mean blood pressure (BP) (from $218.6{pm}6.99$ to $190.0{pm}3.42$ mm Hg, p<0.01). This result indicates that BSP is strong inducer of HO-1 expression, which may be triggered by oxidative stress, and has anti-hypertensive activity.