The benzyl residue in the title compound, C(21)H(23)N(5)·0.5H(2)O, is oriented at a dihedral angle of 83.8 (3)° towards the 1,6-dihydro-imidazo[4,5-d]pyrrolo-[2,3-b]pyridine system. The piperidine ring adopts a chair conformation with the cis substituents displaying a torsion angle of -45.91 (16)°. In the crystal, mol-ecules are accumulated as racemic dimers by two inter-molecular hydrogen bonds between the pyrrolo-pyridine systems. Another hydrogen bond is formed between the imidazole ring and the cocrystallized water mol-ecule, which is located on a twofold rotation axis.