A wavelength conversion module, a method for forming a wavelength conversion module, and a projection device are provided. The wavelength conversion module includes a substrate and a wavelength conversion layer. The wavelength conversion layer is located on the substrate and has a plurality of first holes. The wavelength conversion layer includes a wavelength conversion material, a first bonding material, and a first filling adhesive material. The wavelength conversion material is dispersed in the first bonding material. The first filling adhesive material is configured to fill at least a portion of the first holes. The projection device includes the wavelength conversion module, an excitation light source, a light valve, and a projection lens. The wavelength conversion module provided herein has good conversion efficiency and reliability.