A novel trinuclear complex [Ni₃(μ₃-dbay)₄Cl₂]I₃ (1) with a mixed-valence state was prepared by reacting the tridentate ligand 1,13,14-triaza-dibenz[a,j]anthracene (dibenzanthyridine = dbay) with anhydrous NiCl₂ and sodium tetraphenylborate. The title compound provides the first example of a trinuclear nickel-anthyridine-based string complex in which the metal framework of complex 1 consists of Ni^II–Ni^I–Ni^II. X-ray crystallography, magnetic susceptibility and detailed EPR measurements were performed to characterize the structure and magnetic properties of this unique complex.