Mg-Y2O3 nanocomposites were synthesized by disintegrated melt deposition method (DMD). Tensile tests and constant stress amplitude fatigue tests were carried out on Mg nanocomposites with 0.5, 1.0 and 2.0 volume percentages of reinforcements. Yield strengths of the nanocomposites were found to increase with higher volume fraction of Y2O3. Both unreinforced Mg and the Mg nanocomposites were found to strain harden upon cycling. The hardening behaviour was more intense in the nanocomposites.