Electrocodeposition of alumina nanoparticles and copper thin film on silicon wafers was performed. The volume fraction of the nanoparticle is about 5% and the size is about 50 nm. Comparison between the static tensile behaviors of specimens with and without nanoparticles reveals that the Young's modulus is significantly increased by incorporating nanoparticles into the copper film. However, the ultimate tensile strength of the nanocomposite (235 MPa) is slightly lower than that of the pure copper reference specimen (250 MPa). For the nanocomposite, the strain at failure is 7.8%, which is lower than that of the pure copper film (10.5%). Distinct microscale deformation mechanisms are observed: the main deformation mechanism of the pure copper film is slip followed by strain hardening, whereas for the nanocomposite, multistage failure behaviors are found due to the debonding at the nanoparticle/copper interface. Notched specimens were also tested and compared with the unnotched specimens. In addition, cyclic loading tests on the nanocomposite were conducted to show its hardening behavior.