A novel one-step compression molding was proposed and successfully employed for preparation of closed-cell foams based on natural rubber (NR)/carbon black (CB) composite. The uniqueness of this new method was that both the foam density and expansion ratio became independent of the CB content. The rheometrical findings indicated that the increase in the CB content from 0 to 20 phr yielded a 0.91 and 3.51 N m increase in the initial and the final torque, respectively. The SEM results demonstrated that the prepared foam had three different layers including the skin, transition, and core layers. Almost 14-fold enhancement of the cell density (from 8 to 117 cells/cm(3)) was obtained by increasing the CB content in a constant foam density. Although, curing properties, cell morphology, and mechanical properties of the foam improved by increasing the CB content, the gradual deterioration was observed for sound absorption properties.