Food-grade colloidal particles or complexes made from natural polymers via noncovalent interactions can be good candidates for applications in food and non-food industries. In this work, insoluble chitosan/gelatin-B (CH/GB) complex particles were used for the first time as effective Pickering emulsifiers to make long-term stable oil-in-water emulsions and emulsion gels by one-step homogenization. The CH/GB complexes were only formed in the oppositely charged pH region via electrostatic complexation of CH and GB, and the pH showed a remarkable effect on the surface activity of CH/GB mixed systems. The presence of CH/GB insoluble complexes significantly decreased the surface tension of the oil/water interface, therefore benefitting the formation of smaller emulsion droplet sizes and effectively hindering droplet coalescence, as supported by the increase of emulsion long-term stability. Increasing the oil volume fraction considerably accelerated the formation of a droplet network structure, resulting in a solid-like thermoreversible emulsion gel with tunable viscoelastic properties. Our results suggest that CH/GB insoluble complex particles are promising particulate emulsifiers for the preparation of surfactant-free Pickering emulsions as well as emulsion gels.