Palladium and platinum nanocrystals are synthesized by the liquid−liquid phase transfer method, which is a suitable way to produce anisotropic metallic nanoparticles and control their shape at the nanoscopic scale. The process leading to shape control is, however, quite complex as all the physical and chemical parameters could play an important role. In this paper, we have demonstrated the primordial role of the dissolved gases (O 2 , H 2 , N 2) in the solvent medium on the nanomorphology of platinum and palladium nanocrystals. In particular, it shows the specific role of H 2 in the formation of platinum nanocubes.