In this paper, Mn 2p, Nd 3d and 4d core levels in Nd0.9Sm0.1BaMn2O6 were studied by X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The obtained photoelectron spectra of Mn demonstrate the presence of Mn in oxidation states 3+ and 4+. From the shape of the XES spectrum of the K(3 line of manganese and the presence of the satellite K(3' at energy E = 6476 eV, the spin state of the manganese ion in the compound can be determined. The experimental emission spectra of Mn are compared with the multiplet calculation. The analysis of XPS spectra of the double manganite Nd0.9Sm0.1BaMn2O6 compound shows 3+ and 4+ oxidation states of Mn ions with 2:1 ratio, respectively. The analysis of Mn K(3 XES spectrum of the Nd0.9Sm0.1BaMn2O6 based on multiplet calculations shows the Mn3+/Mn4+ ion ratio to be 1:1, which is often typical for the RBaMn2O6 compounds. The calculation also reveals the high-spin state of Mn3+.