Abstract: This theoretical study focused on the structure of mono-hydroxy derivatives of closo-borate anions and nature of bonding interactions in these species. DFT calculations at the ωB97X-D3/6-31++G(d,p) level of theory have been performed and B–B, B–H, B–O, and O–H bonding interactions in the mono-hydroxy derivatives of closo-borate anions [B_nH_n – 1OH]^2– (n = 6, 10, 12) have been studied under the perspective of the Quantum Theory of Atoms in Molecules (QTAIM) and several local and integral topological properties of the electron density involved in these interactions.