The effect of phosphorus on tungsten oxynitrides has been studied. Phosphorus was introduced via tungsten heteropolyanions. Propene hydrogenation and n-heptane isomerization were used to probe the activity and selectivity of the doped materials. Catalysts were characterized using elemental analysis, X-ray diffraction, N-2 BET surface area, CO chemisorption, and X-ray photoelectron spectroscopy (XPS). Reactivity experiments over P-containing oxynitrides show enhanced hydrogenating properties and decreased n-heptane isomerization. As indicated by XPS measurements, tungsten oxynitrides show higher concentrations of lower W oxidation states on P addition.