This paper reports on room-temperature high-density diamond seeding for low-temperature microwave plasma enhanced chemical vapor deposition of nanocrystalline diamond (NCD) on W/Si substrates. A tungsten layer acts as a diamond nucleation-enhancing layer. Formation of tungsten-carbide (WC) complex increases the initial nucleation density and plays an important role in facilitating diamond growth characteristics. Microwave plasma-enhanced chemical vapor deposition is applied to synthesize diamond films in Ar diluted by methane without hydrogen additives at low temperature. NCD seeding and film formation were investigated as a function of the thickness of tungsten interfacial layer. Raman spectroscopy, SEM, AFM and TEM were applied to characterize NCD films in order to gain insight into the initial stage of NCD diamond synthesis.