We studied the Fe and Mo valence states in Sr2FeMoO6 using x-ray absorption spectroscopy. The experimental results were analyzed using atomic multiplet plus crystal field calculations. The analysis indicates that the Fe ions present a fairly ionic Fe3+ (3d 5) valence, and that the Mo ions are in a strongly covalent Mo5+ (4d 1) state. The presence of Fe ions in a 2+ valence state can be excluded from the Fe-L2,3 spectrum. These results can be understood taking into account the relative energy of the d-levels, the relative strength of the M d - O p mixing, and the exchange stabilization of the Fe3+ ion.