We consider the semileptonic and nonleptonic D_s decay modes to final states with η and η^'. We use QCD sum rules to determine the D_s →η form factor f_+^η, and a generalized factorization ansatz to compute nonleptonic decays. We propose a parameterization of possible OZI suppressed contributions producing the η^' in the final state, compatible with current data; such a scheme can be further constrained improving the precision of the measurement of the D_s decay rates, as expected by the ongoing experiments.