Highly reusable and active silicon‐nanowire‐array‐stabilized metal‐nanoparticle (SiNA‐MNP) catalysts are prepared for effective hydrogenation under mild conditions. Monometallic Pd (SiNA‐Pd), platinum (SiNA‐Pt), and rhodium (SiNA‐Rh) nanoparticles are prepared on silicon nanowire arrays by the silver‐nanoparticle‐assisted chemical etching of silicon wafers with a variety of metal precursors. Moreover, bimetallic Pd−Rh (SiNA‐PdRh) and Pd−Pt (SiNA‐PdPt) nanoalloy catalysts are also synthesized in one‐pot processes in mixed‐metal solutions without any reducing agent, such as NaBH4 or H2 gas, and other external factors. The SiNA‐MNP catalysts were characterized by SEM/EDX, TEM, XAFS, XRD, and ICP‐MS. Each catalyst was used to hydrogenate trans‐stilbene in a 0.1 MPa hydrogen atmosphere to assess catalytic activity. Moreover, the SiNA‐PdPt and SiNA‐PdRh alloy catalysts are also robust and stable, with high reusability numbers for hydrogenation.