Lentil, black soybean, and black turtle bean are rich in phenolic antioxidants but belong to different scientific genera with different protein structures. This study's objective was to compare the characteristics of peptides derived from the protein hydrolysates of these legumes. Proteins were isolated, cooked, and subjected to in vitro digestion with pepsin, trypsin, and chymotrypsin. Hydrolyzed peptides were fractionated by ultrafiltration (UF), anion-exchange chromatography, and gel-permeation chromatography (GPC). GPC-eluted peptides of <
3 kDa with high angiotensin I-converting enzyme (ACE)-inhibitory activities were sequenced. Antioxidant profiles of peptides from the three legumes analyzed by five methods did not follow the same activity patterns associated with the decreases in peptide's molecular size. Among the UF fractions, the <
3 kDa fraction had the highest ACE-inhibition with approximately 45%, 42%, and 39% at 100 µg/mL. Stepwise purifications of the hydrolysates enhanced the ACE-inhibitory capacity (IC