Platinum-based alloys have always been considered as more efficient and economical electrocatalysts for methanol oxidation reaction (MOR) compared with the traditional monometallic Platinum catalysts. Among them, PtCo bimetallic alloys are typical representatives which in many cases display prominent catalytic properties. Herein, rhombic dodecahedral PtCo nanocrystals (PtCo RDs) were obtained by a simple solvothermal method by using ascorbic acid as the reducing agent and cetyltrimethylammonium chloride (CTAC) as the stabilizing and structure-directing agent. The resultant PtCo RDs exhibit remarkably enhanced catalytic activity toward MOR in comparison with the commercial Pt/C catalyst. Its specific and mass activities are 3.8 mA/cm2 and 0.76 A/mg, respectively, which are 6.3 times and 2.5 times that of Pt/C catalyst. Moreover, the PtCo RDs show improved catalytic stability. We hope that this research can provide new insight into the design of catalysts in this field.