This study investigates the effects of latent heat transfer associated with liquid film vaporization on the heat transfer in the laminar mixed convection flows under the simultaneous presence of the combined buoyancy forces of thermal and mass diffusion. Major nondimensional groups identified areGrT, GrM, Re, ϕ, PrandSc. The results specifically present an air‐water system under various conditions. The effects of wetted wall temperature, Reynolds number and relative humidity of the air at the ambient on the momentum, heat and mass transfer are examined in great detail. Results show that the effects of evaporation of the wetted wall on the laminar mixed convection heat transfer are rather substantial.