BACKGROUND Fish gelatin (FG) has multifunctional properties similar to mammalian gelatin (MG), and it has been recognized as the optimal alternative to MG. While its poor surface‐active and gelling properties significantly limit its application values, glycosylation has been successfully used to increase surface‐active properties of FG, but the influence of ultrasonic‐associated glycosylation (UAG) on the gelling and structural characteristics of FG is still rarely reported. This article explores UAG (100–200 W, 0.5–1 h) with κ‐carrageenan (κC) on the functional properties (emulsifying, gelling and rheological properties) and structural characteristics of FG. RESULTS The longer time and higher power of ultrasonics accelerated the glycosylation reaction with an increase in glycosylation degree and browning index values. Compared with original FG, FG–κC mixture and bovine gelatin, UAG‐modified FG possessed higher emulsification activity index, emulsion stability index, gel strength, hardness and melting temperature values. Among them, gelatin modified by appropriate ultrasonic conditions (200 W, 0.5 h) had the highest emulsifying and gelling properties. Rheological results showed that UAG contributed to the gelation process of gelatin with advanced gelation time and endowed it with high viscosity. Structural analysis indicated that UAG promoted κC to link with FG by the formation of covalent and hydrogen bonds, restricting more bound and immobilized water in the gels, exhibiting higher gelling properties. CONCLUSION This work showed that UAG with κC is a promising method to produce high gelling and emulsifying properties of FG that could replace MG. © 2023 Society of Chemical Industry.