The experimental electron density p(r) of Mn-2(CO)(10) was determined by a multipole analysis of accurate X-ray diffraction data at 120 K. The quantum theory of atoms in molecules (QTAM) was applied to p(r) and its Laplacian del(2)p(r). The QTAM analysis of p(r) showed the presence of a bond critical point (r(c)); its associated bond path connects the two Mn atoms, but no cross interaction line was found between one manganese and the equatorial carbonyls of the other. The distribution of del(2)p(r) indicated "closed-shell" interactions for the metallic Mn-Mn bond and the dative Mn-CO bonds. The values of the topological parameters of the density at r(c), p(r(c)), del(2)p(r(c)), G(r(c)) (kinetic energy density), and V(r(c)) (potential energy density), characterize the bonds and are intermediate to those corresponding to typical ionic and covalent bonds.