Abstarct: In the light of recent developments, the issue of increasing the heat transfer in heat exchangers is of major importance for the use of engineering applications. Corrugating channel walls is a way to enhance heat transfer in heat exchangers. In recent years, the nanofluids have been widely used as working fluid in heat exchangers to enhance the system efficiency. In present investigation, the effort is focused on the calculation of entropy generation for nanofluid flow inside wavy channels in mixed convection heat transfer. The simulation is carried out using Fluent commercial software. Firstly, a gird independent study is performed and then the results are compared with similar works in the field. After the validation, the effects of the nanoparticles volume fraction and geometrical parameters of the sinusoidal wavy-wall channel are investigated on the Nusselt number and entropy generation. The parameters are investigated in the range of: nanoparticles volume fraction (0.01<phi<0.05), Richardson number (0.1<Ri<10), wave amplitude ratio (0.1<λ<0.3) and wave length ratio (1<β<3). Results reveal that increasing nanoparticle volume fraction within investigated Richardson number will increase Nusselt number. In addition, the maximum entropy generation rate declines as Richarson number increases. Also, the minimum amount of the entropy generation for β=1,2 occur at λ=0.2 and for β=3 occurs at λ=0.1.