This paper describes the synthesis of Pd-Au bimetallic nanocrystals with controlled morphologies via a one-step seeded-growth method. Two different reducing agents, namely, 1-ascorbic acid and citric acid, were utilized for the reduction of HAuCl4 in an aqueous solution to control the overgrowth of Au on cubic Pd seeds. When 1-ascorbic acid was used as the reducing agent, conformal overgrowth of Au on the Pd nanocubes led to the formation of Pd-Au nanocrystals with a core-shell structure. On the contrary, localized overgrowth of Au was observed when citric acid was used as the reducing agent, producing Pd-Au bimetallic dimers. Through this Morphological control, we were able to tune the localized surface plasmon resonance peaks of Pd-Au bimetallic nanostructures in the visible region.