Flow through diffusers in general is of great importance in many engineering applications. The flow in an asymmetric diffuser has been studied experimentally and numerically. The diffuser has an opening angle of 8 Deg., area ratio of 4.7, and an inlet aspect ratio of 4. Measurements are carried out to determine the diffuser performance with fully developed turbulent flow and wake flow at entry to the diffuser. The experimental results showed significant changes in the velocity profiles and in particular with wake flow inlet condition. Such wake flow leads to deteriorate the diffuser pressure recovery coefficient and an increase in the total pressure loss coefficient. Computation of the turbulent flow through the diffuser has been carried out with ANSYS code using k-ε turbulence model. It is found that the used model is not capable to accurately capture the flow behavior very close to the walls.