The electronic structure of the Tm 3Co 11B 4 compound has been studied by X-ray photoemission spectroscopy and ab initio self-consistent tight binding linear muffin tin orbital (TB LMTO) method. This compound crystallizes in the hexagonal Ce 3Co 11B 4-type structure (P6/mmm). We have found a good agreement between the experimental XPS valence band spectra and theoretical ab initio calculations. The calculated total magnetic moment is equal to 13.635 μ B/f.u. The magnetic moments on the Co atoms are antiparallel to the moments of the Tm atoms. Their values are depended on the local environment, especially on the number of the Co neighbors. The theoretical results are compared with other calculations, saturation magnetization measurements as well as neutron diffraction data for R 3Co 11B 4 (R=Y, Nd, Gd, Tb).