Nanoscale alloys attract enormous research attentions in catalysis, magnetics, plasmonics and so on. Along with multicomponent synergy, quantum confinement and extreme large surface area of nanoalloys offer novel material properties, precisely and broadly tunable with chemical composition and nanoscale dimension. Despite substantial progress of nanoalloy synthesis, the randomized positional arrangement and dimensional/compositional inhomogeneity of nanoalloys remain significant technological challenges for advanced applications. Here we present a generalized route to synthesize single-crystalline intermetallic nanoalloy arrays with dimensional and compositional uniformity via self-assembly. Specific electrostatic association of multiple ionic metal complexes within self-assembled nanodomains of block copolymers generated patterned monodisperse bimetallic/trimetallic nanoalloy arrays consisting of various elements, including Au, Co, Fe, Pd, and Pt. The precise controllability of size, composition, and intermetallic crystalline structure of nanoalloys facilitated tailored synergistic properties, such as accelerated catalytic growth of vertical carbon nanotubes from Fe-Co nanoalloy arrays.