Silica nanoparticles (40 nm) were individually and conformally coated with alumina films using atomic layer deposition (ALD) in a fluidized bed reactor. Films were deposited using self-limiting sequential surface reactions of trimethylaluminum and water. Alumina vibrational modes were observed using Fourier-transform infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) indicated complete coverage on the surface as the silica features were completely attenuated. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed high uniformity of the deposited films. Transmission electron microscopy (TEM) revealed extremely conformal films with an average growth rate of 0.11 nm per cycle. Self-limiting characteristics of ALD allowed primary nanoparticles to be coated as they fluidized as dynamic aggregates.