This letter reports on the tunable wetting behavior of poly(dimethylsiloxane) (PDMS) via the combination of nanostructuring and plasma treatment. The PDMS is first micro/nanostructured by an integrated casting process. Subsequently, an inductively coupled plasma is used to modify the siloxanes' surface chemistry. Sulfur hexafluoride, fluoroform, as well as octafluorocyclobutane plasma were applied to treat PDMS samples successively. By optimizing the treatment parameters, tunable wettability of the siloxane was observed, i.e., superhydrophilicity and superhydrophobicity. The stability of its wetting behavior has been demonstrated after 24 h. This stable and tunable wettability extends the applications of PDMS in microfluidic systems.