The biochemical properties of collagens and gels from grass carp (Ctenopharyngodon idella) were studied to explore the feasibility of their application in biomaterials. The yields of skin collagen (SC) and swim bladder collagen (SBC) extracted from grass carp were 10.41 ± 0.67% and 6.11 ± 0.12% on a wet basis, respectively. Both collagens were characterized as type I collagen. Denaturation temperatures of SC and SBC were 37.41 ± 0.02 °C and 39.82 ± 0.06 °C, respectively. SC and SBC had high fibril formation ability in vitro, and higher values of salinity (NaCl, 0–280 mM) and pH (6–8) in formation solution were found to result in faster self-assembly of SC and SBC fibrils as well as thicker fibrils. Further tests of SC gels with regular morphology revealed that their texture properties and water content were affected by pH and NaCl concentration. The hardness, springiness, and cohesiveness of SC gels increased and the chewiness and water content decreased as pH increased from 7 to 8 and NaCl concentration increased from 140 to 280 mM. These properties suggest that collagens from grass carp may be useful in biomaterial applications in the future.