The red upconversion emission of Ho³⁺ ions, in the optical window of biological tissue, exhibits excellent prospects in biological applications. This study aims to enhance the red upconversion emission intensity of Ho³⁺ ions in NaLuF₄:20%Yb³⁺/2%Ho³⁺/12%Ce³⁺ nanoparticles through building different core–shell structures with different excitation wavelengths. A significantly enhanced red upconversion emission with a higher red-to-green ratio was successfully obtained in NaLuF₄:20%Yb³⁺/2%Ho³⁺/12%Ce³⁺@NaLuF₄ core–shell nanoparticles by introducing the Yb³⁺ and Yb³⁺/Nd³⁺ ions into the NaLuF₄ shell, with enhancement of the red emission occurring when Yb³⁺ and Nd³⁺ ions in the shell transfer more excitation energy to the Ho³⁺ ions. Investigation of the red emission enhancement mechanism is based on spectral characteristics and lifetimes. We examined the synergistic effect of dual-wavelength co-excitation NaLuF₄:20%Yb³⁺/2%Ho³⁺/12%Ce³⁺ @NaLuF₄:10%Yb³⁺/15%Nd³⁺ core–shell nanoparticles to establish optimal excitation conditions. It is hoped that this method, using red upconversion emission core–shell nanoparticles with multi-mode excitation, can provide new ways to expand the applications of rare-earth luminescent materials in biomedicine and anti-counterfeiting.