Effects of protein concentration (4–8%, w/v), inulin concentration (1–5%, w/v) and ionic strength (10–50 mM) on Ca²⁺-induced interactions between whey protein (WP) and inulin mixture (pH 7.0) heated at 85°C for 30 min were investigated. The interactions were analyzed for turbidity, particle size, zeta potential, apparent viscosity, and texture profile. Interaction properties were also compared with mixture of polymerized whey protein (PWP) and inulin in which whey protein was heated first and then mixed with inulin. Results indicated that the dispersion became more opaque with increasing protein but no significant difference was detected regarding the way inulin added (P < 0.05). Three peaks at about 40, 900 and 5000 nm were observed in size distribution by volume. Compared with the control, there was a small shift toward larger size with increasing inulin level in the width of peak corresponding to denatured whey protein. Zeta potential values for all samples fell in the ranges of −10 to −30 mV independent of the manner in which inulin added. Increasing inulin resulted in less negative zeta potential and smaller repulsive force between particles for both types of mixtures. As protein and inulin increased, apparent viscosity increased and combination of PWP and inulin showed significant higher values (P < 0.05) than WP and inulin mixture. It was not sufficient to form cold gels for all samples at the level of 10 mM Ca²⁺. Compared with the control, the mixtures of PWP with inulin showed higher water holding capacity may due to the ability of occluding water of inulin microcrystals (P < 0.05). WP/inulin mixture showed significant higher hardness (P < 0.05) than PWP/inulin due to possible microcrystal seeds maintained in solutions when heated at 80°C for 30 min. Results indicated that interactions maybe occurred between whey protein and inulin in the model system.