We present ferromagnetic resonance (FMR) and magnetic properties of single domain Y3Fe5O12 (YIG) nanoparticles with an average size of 60nm. The saturation magnetization shows a diminution of practically 13 of the bulk magnetization due to the surface/volume contribution. The coercive force vs. temperature indicates that the particles are single magnetic domains in the blocked state. The FMR data, confirm this state below 350K. Data of DC-magnetization, magnetic resonance field and linewidth of the FMR spectra are presented. Shape, surface and dipolar contributions to effective anisotropy are discussed.