Yittrium iron garnet, Y 3 Fe 5 O 12 (YIG), is a material used widely in electronic devices for the microwave region as well as the magnetic bubble domain-type memories. Yittrium iron garnet (Y 3 Fe 5 O 12 ) was produced by mechanochemical synthesis from Y 2 O 3 and Fe 2 O 3 with a particle size of around 150nm. Dense ceramics with theoretical density of around 95% was obtained from mechanochemically activated powders after sintering at 1425°C for 10h without calcination step. Ferro-magnetic resonance (FMR) spectrum and microwave absorption spectrum of the YIG nanoparticles were studied at different frequencies and magnetic fields. The signal exhibits a resonance character at each frequency. It was observed that the location of the FMR signal peak at the field axes monotonically shifts to higher field with increasing frequency. The dielectric properties of YIG pellets produced from nanopowder was studied over a wide range of frequency and as a function of temperature. It was observed that the dielectric constant, dielectric loss and electrical conductivity gradually increase with temperature.