The solid-state structure of the title compound, [Na(2)Mn(2)(C(32)H(56)N(2)OSi(2))(2)O(2)] or [1,8-C(10)H(6)(NSi(i)Pr(3))(2)Mn(mu(3)-O)Na(THF)](2), which lies across a crystallographic twofold axis, exhibits a central [Mn(2)O(2)Na(2)](4+) core, with two oxide groups, each triply bridging between the two Mn(III) ions and an Na(+) ion. Additional coordination is provided to each Mn(III) centre by a 1,8-C(10)H(6)(NSi(i)Pr(3))(2) [1,8-bis(triisopropylsilylamido)naphthalene] ligand and to the Na(+) centres by a tetrahydrofuran molecule. The presence of an additional Na...H-C agostic interaction potentially contributes to the distortion around the bridging oxide group.