A new alluaudite-group mineral zincobradaczekite, a Zn–Cu ordered highly zincian analogue of bradaczekite, was discovered in sublimates of the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with bradaczekite, lammerite, lammerite-β, borisenkoite, mcbirneyite, sanidine, hematite, tenorite, pseudolyonsite, lyonsite, starovaite, rutile, tripuhyite, pseudobrookite, piypite, langbeinite, calciolangbeinite, aphthitalite, alumoklyuchevskite, and palmierite. Zincobradaczekite forms oblique-angled prismatic crystals up to 0.02 × 0.02 × 0.08 mm³ and equant or tabular crystals up to 0.05 mm. It is transparent, blue, greenish-blue, grey-blue or bluish-grey. The lustre is vitreous. D_calc is 4.71 g cm⁻³. Zincobradaczekite is optically biaxial (–), α 1.786(5), β 1.846(8), γ 1.90(1), 2V_meas. 80(5)º. Chemical composition (wt%, electron microprobe) is Na₂O 4.07, K₂O 0.53, CaO 0.01, MgO 0.71, MnO 0.01, CuO 19.89, ZnO 24.21, Al₂O₃ 0.02, Fe₂O₃ 0.90, TiO₂ 0.03, P₂O₅ 0.41, V₂O₅ 1.05, As₂O₅ 47.10, SO₃ 1.01, and total 99.95. The empirical formula based on 12 O apfu is Na_0.90K_0.08Cu_1.70Mg_0.12Zn_2.03Fe³⁺_0.08(As_2.79S_0.09V_0.08P_0.04)_Σ3.00O₁₂. The simplified chemical formula is NaCu₂Zn₂(AsO₄)₃. Zincobradaczekite is monoclinic, C2/c, a 12.0375(13), b 12.4500(13), c 7.2213(8) Å, β 117.506(7)º, V 959.90(18) ų and Z 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are 6.21(31)(020), 3.416(70)(310, − 112), 3.200(17)(002), 2.779(23)(− 402), 2.691(100)(− 132, 240), 1.841(20)(152) and 1.680(14)(− 642). The crystal structure was solved (single-crystal XRD, R = 4.38%). The simplified crystal chemical formula is ^A(1)□^A(1)ʹCu^A(2)□^A(2)ʹNa^M(1)Cu^M(2)Zn₂(AsO₄)₃ (□—vacancy) and the end-member formula is NaCuCuZn₂(AsO₄)₃. Zincobradaczekite and bradaczekite, ideally NaCuCuCu₂(AsO₄)₃, are isostructural. In the Yadovitaya fumarole, Mg-poor bradaczekite forms an isomorphous series with zincobradaczekite, whilst in the neighbouring Arsenatnaya fumarole only a Zn-depleted and Mg-enriched variety of bradaczekite occurs. Zincobradaczekite and bradaczekite differ from other anhydrous alluaudite-group arsenates by increased values of the c and β unit-cell parameters due to the strong Jahn–Teller distortion of M(1)O₆ octahedron predominantly occupied with Cu²⁺.