The optical diffusion of transmitted or reflected light via a deformable wrinkled surface with a periodicity in the range of hundreds of micrometers is studied. Without strain, the sample shows no wrinkles and no optical diffusion. With uniaxial strain, the surface shows aligned wrinkles and anisotropically diffuses incident light in a manner that depends on the degree of applied strain. The relationship between the sinusoidal microstructure and the diffused state is successfully explained in the context of geometric optics. The present system can be used as a mechanically tunable optical diffuser.