•Locust bean gum/κ-Carrageenan (LBG/κ-C) blends synergy verification.•Physicochemical properties of films and capsules were improved by LBG.•Storage ability and brittleness of hard capsules were improved by LBG.•LBG/κ-C blends at 1:3 ratio can successfully prepare hard capsules.A novel gelling agent, comprising blended κ-carrageenan (κ-C), a seaweed polysaccharide and locust bean gum (LBG), was used to prepare hard capsules. The distinct synergism between κ-C and LBG were verified by the textural profile analysis (TPA), FTIR and rheological measurement. Afterwards, films and hard capsules were prepared with the optimized LBG/κ-C blend gel. And the mechanical properties and morphology of films and hard capsules were analyzed by tensile testing and SEM, respectively. The results showed that the LBG/κ-C at 1:3 ratio could serve as an excellent gelling agent, which endowed hard capsule with the promoted mechanical properties, homogenous and smooth surface morphology. This work suggests that a novel blended LBG/κ-C gelling agent successfully prepared for hard capsules with improving physicochemical properties.