Superplastic behavior of heavily drawn Cu–at.% Ag filamentary microcomposite wires was investigated. The filamentary microstructure tended to break up at high temperatures by spheroidization, grooving, and/or recrystallization because of its high interface energy and high cold-work energy. Above 400 °C, extensive recrystallization occurred and the grains 300–500 nm in size were observed in the Cu matrix. As the deformation proceeded, the elongated silver lamellae and/or the region with numerous filaments broke up and rearranged into chevron patterns, which mostly lay perpendicular to the loading axis. The elongation up to 1000% was obtained at 500 °C at the strain rates of 7 × 10−4/s and −3 × 10−3/s, and the elongation up to 600% was obtained at 400 °C at the strain rate of 1 × 10−4/s. Arrays of dislocations in the matrix and near grain and phase boundaries were observed after superplastic deformation, supporting the slip-accommodated grain and/or phase boundary sliding.