We report the synthesis and characterization of NiSn dendrimer-encapsulated nanoparticles (DENs) with sizes in the range of similar to 1.2 nm. These types of materials have potential applications in energy storage, and particles in the 1-3 nm size range are particularly attractive for this use. The NiSn DENs described here contain an average of 147 atoms and are encapsulated within hydrophobic, sixth-generation poly(amidoamine) dendrimers. DENs prepared using four different Ni/Sn ratios, along with monometallic Ni and Sn DENs, are described. To prevent oxidation, the synthesis was carried out under dry conditions in toluene. These bimetallic DENs were characterized by UV-vis spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicate that the compositions of the nanoparticles reflect the ratio of Ni2+ and Sn2+ used in the first step of the synthesis; the NiSn nanoparticles remain encapsulated within the dendrimers, and when dry they have a degree of stability even after a short exposure to air.