Tailored morphology of porous binary Pt-based nanostructures is a powerful way to improve their catalytic properties. Herein, we develop a facile aqueous solution approach for the rational one-step synthesis of PtAg nanochains via direct nucleation followed by the oriented attachment growth mechanism under sonication at room temperature. This allows the green and simple fabrication of PtAg wavy nanochains (200 nm length and 20 nm width) with spatially interconnected pores (10 nm) and a high surface area (55.02 m2/g). These merits endowed the methanol oxidation reaction (MOR) performance of PtAg nanochains with a mass activity of (1.12 mA/µgPt) that was about 1.83, 2.8, and 3.11 times higher than those of PtAg nanodendrites, Pt nanodendrites, and commercial Pt/C, respectively, owing to porous nanochain morphology and alloying effect. Intriguingly, visible-light irradiation enhances the MOR performance of PtAg nanochain by nearly 1.5 times, owing to its great photoelectric response properties. The MOR activity of PtAg nanochains is among the highest reported Pt-based electrocatalysts. The presented method may open new edges on the rational design of porous Pt-based nanoarchitecture for various catalytic applications.