In this work, FePt–Au heterostructured nanocrystals (HNCs) such as tadpole-, dumbbell-, bead-, and necklace-like nanostructures were synthesized by a facile heteroepitaxial growth of Au NCs onto FePt nanorods (NRs). A study of the growth mechanism revealed that the morphology control of the final products can be correlated with the adsorption sites of hydrogen onto the FePt NRs, which can be manipulated by the amount of the forming gas (Ar/7% H₂) added. Not only the optical characteristic and magnetic properties of the intrinsic materials were retained in the products, but also the FePt–Au HNCs showed the tunable multifunctional properties resulted from the interactions between Au and FePt. Moreover, for methanol oxidation, the FePt–Au HNCs exhibited enhanced catalytic activity and CO tolerance on the catalyst surface compared to commercial Pt catalysts. It is worth noting that as multifunctional units, the FePt–Au HNCs also possess a heterogeneous surface, which could potentially enable their site-specific functionalization for targeting or imaging purposes in biomedical applications. More interestingly, the catalytic properties of the FePt–Au HNCs also endow this material with application potentials in nanocatalysis.