The design and synthesis of novel three-dimensional (3-D) supramolecular dendrimers is described. The coordination-driven self-assembly of a 120 degrees diplatinum acceptor and tritopic pyridyl donors bearing [G-0]-[G-3] Fréchet-type dendrons results in a series of supramolecular dendrimers under mild conditions, possessing a robust adamantanoid core of well-defined shape and size. The assemblies were identified using multinuclear ((31)P and (1)H) NMR spectroscopy and electrospray ionization mass spectrometry, as well as pulsed-field-gradient spin-echo (PGSE) NMR measurement together with computational simulations. Isotopically resolved mass spectral data support the existence of the [6 + 4] assembly of adamantanoid dendrimers, and the NMR results are consistent with the formation of these symmetrical assemblies. PGSE NMR measurements together with MMFF force-field modeling clearly reveal the structural feature of the 3-D supramolecular dendrimers with varying sizes.