The scattering of time‐harmonic spherical scalar waves by a large, convex, and lossy object with a statistically corrugated surface is considered. The maximum deviation of the corrugated surface from the smooth one is assumed to be small, and hence the boundary‐perturbation technique is used in this study. First, the scattering of scalar waves by a large lossy sphere with statistical surface irregularities is treated as a canonical problem in the general discussion. After the effective reflection coefficient is derived for the sphere case, the asymptotic expressions of mean values of the scattered wave function and the scattered intensity are obtained for the general problem.