A wavelength conversion module and a projection device are provided. The wavelength conversion module includes a substrate, a wavelength conversion layer and a thermal conductive adhesive layer. The wavelength conversion layer is located on the substrate. The thermal conductive adhesive layer is located between the wavelength conversion layer and the substrate. The thermal conductive adhesive layer includes a plurality of particles, the particles are distributed in the thermal conductive adhesive layer, and a particle concentration of the particles has a volume ratio greater than 0% and less than or equal to 80%.