Two dinuclear nickel amine‐selenolate complexes of the tridentate amine‐selenolate ligand, 4‐tert‐butyl‐2,6‐di(aminomethyl)selenophenol (1b), have been synthesized and their properties characterized. The green complex [NiII2(1b)3]Cl (4a) is readily prepared from 1b, NiCl2 · 6 H2O, and NaOMe in methanol or by reaction of coordinatively unsaturated [NiII2(1b)2][BPh4]2 (2b) with another one equivalent of 1b in the presence of triethylamine. The face‐sharing, bioctahedral structure of 4a is derived from UV/Vis spectroscopy, cyclic voltammetry, and single‐crystal X‐ray diffraction of its oxidation product, [NiIINiIII(1b)3]2+. The dication was prepared by air‐oxidation of 4a in MeOH and isolated as the dark‐brown BPh4− salt, [NiIINiIII(1b)3][BPh4]2 · CH3OH (4b). Mixed‐valent complex 4b consists of a dinuclear, face‐sharing bioctahedral dication with a central N3NiII(μ2‐SeR)3NiIIIN3 core and well‐separated tetraphenylborate anions. Distortions from D3h symmetry suggest that 4b is a trapped‐valence compound in the solid‐state. On the CV time scale complex 4a undergoes two reversible one‐electron oxidations at E11/2 = –0.15 and at E21/2 = +0.29 V vs SCE, affording 4b and the thermally not stable trication [NiIII2(1b)3]3+, respectively. The EPR spectrum of a powdered sample of 4b reveals an S = 3/2 ground state of the mixed‐valent NiIINiIII complex.