The compound Bi_{7 - δ}Ni₂Br _{5 - 2δ} = (Bi₃Ni)₂[Bi _{1 - δ} Br₄]Br_{1 -2δ} (δ = 1/9) is a sub-bromide of the intermetallic phase Bi₃Ni. Its crystal structure contains metallic rods,∞¹ [Bi₃Ni], which are embedded in a salt-like matrix of bromido-bismuthate(III) and bromide anions. The non-stoichiometry originates from the variation of the number n of trans edge-sharing octahedra in the [Bi_n Br_{4n + 2}] ^{(n + 2)-} oligomers (3 ≤ n ≤ 5), as well as from vacancies on the sites of the isolated Br atoms. The simplified structure is described in the orthorhombic space group Cmcm with a = 4.0660 (4), b = 23.305 (3), c = 17.130 (2) Å. It shows a statistical distribution of vacancies and orientational disorder of the concatenated octahedra. By choosing the modulation vector q = a^*/9 + b^*/2, the additional weak reflections of the diffraction pattern can be indexed. In the [3 + 1]-dimensional superspace group Pmnm(α1/20)000, an ordered structure model is achieved. The modulated crystal structure bears a strong resemblance to the somewhat higher oxidized sub-bromide Bi_{7 - δ}Ni₂Br₅ (δ = 1/9).