A numerical study of transient natural convection heat and mass transfer along a vertical complex wavy surface has been performed. A complex wavy surface was created from two sinusoidal functions, a fundamental wave and its first harmonic. The complex wavy surface is maintained at uniform wall temperature and constant wall concentration. An implicit finite-difference scheme is used for analysis. The numerical results demonstrate that the additional harmonic substantially alters the flow field, temperature and concentration distribution near the surface. Also the numerical results show that the local heat and mass transfer rate for a complex surface are smaller than of a flat plate. This decreased local heat and mass transfer rate seems to depend on the ratio of amplitude surface. پرونده مقاله