In the cation of the title compound, C(21)H(16)N(3)O(2) (+)·NO(3) (-), the N atom in the 3-position of the imidazole ring is protonated. The three pendant aromatic rings are twisted from the plane of the imidazolium ring by dihedral angles of 22.75 (1), 79.63 (1) and 29.65 (1)°. In the crystal structure, N-H⋯O hydrogen bonds link the mol-ecules, forming an infinite one-dimensional chain parallel to the b axis.