In this study, experimental tests, together with computer analyses, were carried out to identify the essential nutritional markers that can offer protein supplementation-based nutrition support for hypertension. In particular, 16 marine shellfish proteins were firstly screened for in silico hydrolysis by gastrointestinal enzymes and then the binding abilities of the obtained oligopeptides to angiotensin-converting enzyme (ACE) were examined. In addition, the ACE inhibition activities of selected oligopeptides were assayed in vitro. It was discovered that mussel-derived NADH dehydrogenase and AMP-activated protein kinase and razor-clam-derived cytochrome b, NADH dehydrogenase, and ATP synthase were excellent sources of protein that are able to release a high amount of ACE-binding peptides. Meanwhile, four oligopeptides (SCCGY, SSGAW, PICQF, and IQPEW) were detected as strong ACE binders, with IC50 values of 0.09, 0.25, 0.41, and 0.60 mM, respectively. Therefore, our findings demonstrate that shellfish proteins can serve as nutritional support for hypertension when patients are supplemented with these markers. In particular, oligopeptides are identified as the most promising compounds.