This work discussed the catalytic performance towards CO oxidation over unsupported nanoporous Ag (np-Ag) catalysts synthesized by dealloying of Mg77Ag23 (at.%) alloy under controllable etching conditions. The np-Ag catalysts were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The np-Ag catalysts exhibit an open, bicontinuous interpenetrating ligament-channel structure. The np-Ag samples fabricated under different conditions possess distinct feature sizes ranging from similar to 15.7 to similar to 142.6 nm. Without any heat-treatment, the asobtained np-Ag catalysts were utilized for catalysis tests. The results reveal that the catalytic activity of the unsupported np-Ag catalysts is comparable with or even better than that of supported Ag catalysts with heat-treatment. In addition, the role of residual Mg and feature size in the catalytic activity of the np-Ag catalysts has been clarified. The catalytic mechanism of the present unsupported np-Ag catalysts has also been discussed. (C) 2013 Elsevier B.V. All rights reserved.