Acid-soluble collagen(ASC) and pepsin-soluble collagen(PSC) from the spine(ASC-SP and PSC-SP) and skull(ASC-SK and PSC-SK) of the skipjack tuna, Katsuwonus pelamis, were successfully isolated and characterized. The yields of ASC-SP, PSC-SP, ASC-SK and PSC-SK were(2.47 ± 0.39)%,(5.62 ± 0.82)%,(3.57 ± 0.40)%, and(6.71 ± 0.81)%, respectively, on the basis of dry weight. The four collagens contained Gly(330.2-339.1 residues/1 000 residues) as the major amino acid, and their imino acid contents were between 168.8 and 178.2 residues/1 000 residues. Amino acid composition, SDS-PAGE, and FTIR investigations confirmed that ASC-SP and ASC-SK were mainly composed of type I collagen, and had higher contents of high-molecular weight cross-links than those of PSC-SK and PSC-SP. The FTIR investigation also certified all the collagens had triple helical structure. The denaturation temperatures of ASC-SK, PSC-SK, ASC-SP, and PSC-SP were 17.8, 16.6, 17.6, and 16.5 °C, respectively. All isolated collagens were soluble at acidic pH(1-5) and lost their solubilities when the NaCl concentration was above 2%(W/V). The isolated collagens from the spines and skulls of skipjack tuna could serve as an alternative source of collagens for further application in food, cosmetic, biomedical, and pharmaceutical industries. Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) from the spine (ASC-SP and PSC-SP) and skull (ASC-SK and PSC-SK) of the skipjack tuna, Katsuwonus pelamis, were successfully isolated and The yields of ASC-SP, PSC-SP, ASC-SK and PSC-SK were 2.47 ± 0.39%, 5.62 ± 0.82%, 3.57 ± 0.40% and 6.71 ± 0.81% respectively, on the basis of dry weight. The four collagens contained Gly (330.2-339.1 residues / 1000 residues) as the major amino acid, and their imino acid contents were between 168.8 and 178.2 residues / 1000 residues. Amino acid composition, SDS-PAGE, and FTIR investigations confirmed that ASC-SP and ASC-SK were mainly composed of type I collagen, and had higher contents of high-molecular weight cross-links than those of PSC-SK and PSC-SP. The FTIR investigation The denaturation temperatures of ASC-SK, PSC-SK, ASC-SP, and PSC-SP were 17.8, 16.6, 17.6, and 16.5 ° C, respectively. All isolated col lagens were soluble at acidic pH (1-5) and lost their solubilities when the NaCl concentration was above 2% (w / v). The isolated collagens from the spines and skulls of skipjack tuna could serve as an alternative source of collagens for further application in food, cosmetic, biomedical, and pharmaceutical industries.