To enhance the surface protection of the bimodal Mo-Si-B alloy and simultaneously maintain its superior mechanical properties, a multilayered coating (MoSi₂, Mo₅Si₃ and Mo₅SiB₂/MoB) was synthesized on its surface via pack cementation. Results show that, compared to the coating on the fine-grained substrate, the coating surface on the bimodal substrate is rougher and exhibits bimodal microstructure. Additionally, the fracture toughness of bimodal alloy after coating is acceptable. The distributed La₂O₃ particles toughen the coating. Besides, the coated bimodal specimens show excellent oxidation resistance at 1100~1300 °C, which is attributed to the quick formation of a thin and self-healing SiO₂-B₂O₃ film on the coating surface. With increasing the temperature, the thickness of SiO₂-B₂O₃ film and the oxidation product Mo₅Si₃ increase because the viscosity of SiO₂-B₂O₃ film decreases. Also, improving temperature promotes the interdiffusion of Si and B, accelerating the growth of Mo₅Si₃ and Mo₅SiB₂/MoB layers. Compared to the coated bimodal alloy, the coated fine-grained alloy exhibits more oxidation mass gain at 1300 °C since the unimodal MoSi₂ coating has more grain boundaries.