The new alluaudite-group mineral parabezeliite was found in the Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. In the deepest zone of Arsenatnaya, paraberzeliite (holotype) is accociated with anhydrite, diopside, hematite, svabite, berzeliite, schäferite, calciojohillerite, magnesioferrite, ludwigite, fluorapatite, powellite, baryte, and rhabdoborite-group and aphthitalite-group members. In the middle zone of the fumarole, paraberzeliite occurs with hematite, calciojohillerite, badalovite, johillerite, nickenichite, tilasite, svabite, fluorophlogopite, sanidine, cassiterite, anhydrite, metathénardite and belomarinaite. Paraberzeliite forms prismatic crystals up to 0.2 × 0.2 × 1 mm³often occurring in open-work aggregates. It is transparent, brown (from light to dark brown, sometimes with purple or red hue) or green (from pale greenish to yellow-green). The mineral is brittle, cleavage was not observed. The Mohs hardness is 3 1/2. D_calcis 3.811 g cm^-3. Paraberzeliite is optically biaxial (+), α = 1.718(4), β = 1.728(4), γ = 1.742(4), 2V_meas. = 85(5)°. The chemical composition (wt.%, electron-microprobe; holotype) is: Na₂O 6.43, CaO 16.65, MgO 11.64, MnO 1.65, CuO 0.06, Fe₂O₃2.45, V₂O₅1.10, As₂O₅59.46, total 99.44. The calculated empirical formula based on 12 O atoms per formula unit is (Na_1.20Ca_1.71Mg_1.66Mn_0.13Fe³⁺_0.18)_Σ4.88(As_2.98V_0.07)_Σ3.05O₁₂. Paraberzeliite is monoclinic, C2/c, a = 12.3143(7), b = 13.0679(5), c = 6.7717(4) Å, β = 113.657(7)°, V = 998.14(10) ųand Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data, R = 0.0349. Paraberzeliite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is ^A(1)Ca^A(2)'Na^M(1)Ca^M(2)Mg₂(^TAsO₄)₃. The idealized formula is NaCa₂Mg₂(AsO₄)₃, or, according to the actual nomenclature of alluaudite-group arsenates, NaCaCaMg₂(AsO₄)₃. The name paraberzeliite reflects the dimorphism of this alluaudite-group mineral with the arsenate garnet berzeliite, ideally (Ca₂Na)Mg₂(AsO₄)₃