This paper describes the synthesis and crystal phase behavior of platinum lead nanorods. Both face-centered cubic (fcc) Pt100−xPbx (x < 50) and hexagonally close-packed (hcp) Pt50Pb50 nanostructures are synthesized at mild reaction temperatures (180–200 °C). The crystal phase and composition of these PtPb nanorods can be controlled by changing the reaction time and temperature. A mechanism for the formation of either kinetically or thermodynamically stable PtPb nanorods is discussed. The approach developed for controlling crystal phases at fairly low temperatures can be important for the design of alloy or intermetallic nanostructures for a broader range of applications.