High‐purity mullite powders (3Al2O3.2SiO2) have been prepared using a high‐temperature aerosol decomposition technique yielding submicrometer (0.6 μm average) particles of spherical morphology with no hard agglomerates using aluminum nitrate and fumed silica as precursors. Depending upon the reaction conditions used, the powders range from amorphous to crystalline with no evidence of secondary‐phase formation. This mullite synthesis approach has the advantages of not requiring postsynthesis milling, the ability to use a wide range of precursor systems, and enhanced control over chemical homogeneity and particle size