The invention relates to a method of preparing metallic nanoparticles and to the materials thus obtained. More specifically, the invention relates to a method of preparing metallic nanoparticles consisting in: selecting a precursor from the salts, hydroxides and oxides of metallic elements that can be reduced at temperatures below the clay silicate network destruction temperature; and depositing said precursor on a support selected from pseudolaminar phyllosilicate clays. According to the invention the method comprises: (i) a deposition step in which the precursor is deposited on the support: (ii) when the precursor is selected from among salts and hydroxides, a thermal decomposition step in a controlled atmosphere, in which the precursor is subjected to a decomposition process and is transformed into an oxide of the metallic element: and (iii) a reduction step in which the oxide of the metallic element is subjected to a reduction process in a controlled atmosphere. The aforementioned method is performed at temperatures below the clay silicate network destruction temperature.