Yttrium iron garnet (YIG) particles were first synthesized using a low-temperature method based on the citrate gel process. The annealing temperature dependence of the magnetic behaviour was investigated by means of transmission Fe-57 Mossbauer spectrometry and DC magnetic measurements. The as-prepared particles behaves as an amorphous-like structure. Annealing treatments cause aggregation and crystallization of particles. For low annealing temperatures, one can suggest a nanostructured behaviour of the YIG particles, which progressively disappears when the annealing temperature increases. Depending on the annealing temperature, YIG nanostructured particles of different size, in the range 50-700 nm were obtained. The values of the saturation magnetization as well as the Curie temperature for the YIG particles are close to those observed for well-crystallized YIG.