The reaction of [RuCl(C(9)H(10)BN(6))(C(18)H(15)P)(2)] with benzo-phenone imine in methanol, in the presence of sodium azide, leads to the formation of the title compound, [Ru(C(9)H(10)BN(6))(N(3))(HN=CPh(2))(C(18)H(15)P)]·C(4)H(10)O, which crystallizes as the diethyl ether solvate. In the crystal structure, the Ru atom is coordinated by three N atoms of one hydridotris(pyrazoly)borate anion, one P atom of one triphenyl-phosphine ligand, one N atom of the azide anion and one N atom of the benzophenone-imine ligand in a slightly distorted octa-hedral geometry. The azide anion is almost linear [177.0 (5)°], with an Ru-N-N angle of 125.9 (3)°. There is a small difference between the N-N distances [1.200 (5) and 1.164 (5) Å], the longer bond being adjacent to the Ru atom.