Artifact-free bulk nanocrystalline Cu88Al11.5Y0.5 alloy has been synthesized by in situ consolidation of mechanically alloyed powder blend followed by annealing of the consolidated compact at 200 °C (or 0.35 Tm) for 30 min. Grain size determination and phase identification have been carried by X-ray line broadening analysis and transmission electron microscopy (TEM). Hardness measurement has demonstrated that the Hall-Petch effect is the dominant strengthening mechanism for both as-consolidated and annealed specimens. Strength improvement after short annealing time was attributed to the relaxations of non-equilibrium grain boundaries.