Fish gelatin (FG) and kappa-carrageenan (KC) were mixed to simulate the physicochemical properties of porcine gelatin (PG). The effects of the mixing ratio between FG and KC on the interaction, structure, and rheological properties of FG were investigated. The maximum associative interaction occurred at the critical mixing ratio of KC:FG (w/w) at 4:96, where the median particle size (D-50) of the FG-KC coacervates was 1168 +/- 175 nm, and the zeta potential was -3.8 +/- 0.8 mV. Interestingly, the rheological properties of the mixed gel (KC:FG at 4:96) matched those of PG, including the melting temperature (T-m), gelling temperature (T-g), dynamic consistency factor (K-f), and instantaneous compliance (J(0)). The relationship between structure and physicochemical properties was proposed as a schematic model. The associative interaction between FG and KC was critical for FG's modification and could be applied to improve FG's rheological properties towards PG.