Smooth hound alkaline proteases were used to generate protein hydrolysates from four marine organisms: Triggerfish, Boops boops, smooth hound and cuttlefish. The same hydrolysis degree was reached for all the hydrolysates (DH = 20%). The hydrolysates were compared according to their composition (proximate size and amino acids (AA)), and their antioxidant properties. Also, an assessment of their nutritional value was made. All hydrolysates contained high level of essential, alkaline, hydrophobic, and branched-chain AA, and molecular weight fraction less than 3 KDa was predominant in all hydrolysates (83-93%). Different in vitro antioxidant properties were assayed: the inhibition of linoleic acid autoxidation, β–carotene bleaching, the scavenging effect on α,α-diphenyl-β-picrylhydrazyl free radical (DPPH), Ferrous (Fe²⁺) ion chelating ability and the reducing power. All prepared hydrolysates possessed noticeable antioxidant activities. All hydrolysates of the present study could improve both the quality of food products and the health of the body by improving their respective proteinic and antioxidant status. The cuttlefish hydrolysate exhibited the highest content of essential and branched chain amino acids; hence it is the most interesting hydrolysate in terms of nutritional quality. The highest antioxidant activities were detected in the B. boops hydrolysate. The results of this study suggest that protein hydrolysates of marine origin are good sources of natural antioxidants and amino acids.