We report a facile method for preparing a silica (SiO2)-based material containing Sn nanoparticles (NPs) distributed inside for enhancing the thermal cyclic stability of the inserted Sn NPs. Absorption of a Sn precursor (i.e., an aqueous SnCl2 solution) into a mesoporous SiO2 matrix resulted in confinement of the Sn precursor in a mesoporous SiO2 matrix. Hydrogen thermal reduction of the above composite yielded Sn nanoparticles with a diameter of ca. 30 nm uniformly distributed inside porous SiO2 (p-SiO2) spheres: Sn NPs@p-SiO2. Our investigation of the transformation ofthe porous SiO2 structure to hold Sn NPs revealed that the process was closely related to the transformation of the amorphous hydrolyzed Sn precursor into Sn oxides followed by, probably, the rearrangement of the SiO2 matrix via its interaction with the melting Sn. This led to the formation of stable Sn NPs@p-SiO2. The SiO2 matrix effectively prevented the coalescence of the Sn NPs, and the obtained product exhibited negligible changes in melting behavior during the second to 100th cycle of a freeze melt cycle test.