FeCo nanoparticles are synthesized using a radio frequency (RF) plasma torch. These alloy nanoparticles (~50 nm diameter) are nucleated in the gas phase from a vapor produced by evaporating much larger metal powder precursors (~10 µm diameter) in the thermal plasma. To study the effects of precursor homogeneity on the synthesis, two different starting materials were used: (1) pre-alloyed FeCo powder produced by inert gas atomization, and (2) a mixture of commercial elemental Fe and Co powders. X-ray powder diffraction, SEM, TEM, and x-ray microanalysis were used to characterize the morphology, structure, and chemical homogeneity of the precursors and products. Both starting materials produced alloy product, but nanoparticles produced from pre-alloyed precursors exhibit smaller variations in Fe/Co ratio than particles produced from elemental powders.