This paper presents a new method of synthesis, mechanochemical activation, for the preparation of the Sr3Ti2O7 Ruddlesden-Popper (RP) phase. The results obtained from different starting reagents (SrO, SrCO3, or Sr(OH)(2).8H2O and TiO2 anatase) and mechanical activation systems (vibrating and planetary mills) are compared. An optimized protocol is established that permits one to avoid the high temperatures and long reaction times needed in the classical solid-state reaction method; as a byproduct, very pure phases with controlled particle sizes are isolated as well. The products were studied by X-ray diffraction at room temperature and above, thermal analysis techniques, infrared spectroscopy, and scanning electron microscopy. The insight obtained in this work can be extrapolated to other Sr-2[Srn-1TinO3n+1] Ruddlesden-Popper materials that have not been isolated, until now, as single phases,