Sodium borohydride (NaBH₄) is a vital inorganic reducing agent widely used in organic synthesis, pharmaceutical manufacturing, environmental remediation, and new energy applications. However, NaBH₄ is highly hygroscopic and tends to agglomerate and hydrolyze during storage, leading to reduced reactivity and potential safety hazards, which significantly restrict its practical use in industry and research. In this work, eicosanol was employed as a surface coating agent to suppress the hygroscopicity of NaBH₄. A uniform coating layer was formed on the surface of NaBH₄ via a liquid-phase coating strategy, isolating it from direct contact with moisture. Experimental results demonstrate that the coating effectively reduces the moisture absorption rate from 82.93% to 47.57%, corresponding to a 42.64% reduction. The coated samples retain their original crystal structure and physical stability, without evident agglomeration or structural deterioration. Surface coating with eicosanol can effectively inhibit the moisture absorption of NaBH₄, providing a new approach for extending its storage life and improving its application potential.