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Ni-Mn nanocomposite reinforced by Al₂O₃ particles was fabricated by pulse electrodeposition. The average grain size is 60 nm and the content of Mn and Al₂O₃ particles is 0.3 and 0.6 wt pct, respectively. The superplastic deformation behavior was further studied at the temperatures ranging from 673 to 873 K. A maximum elongation of 530% is obtained in the tension test at a temperature of 773 K and at a strain rate of 1.67×10^-3 s^-1. The curves of the flow stress vs strain rate have features similar to the trend of conventional superplastic materials. The test temperature (773 K) equals to 0.35T_m, which means the material obtains low temperature superplasticity. The microstructures of the composite were examined and grain growth was observed during deformation.