A new 3d transition-metal molybdate-tellurite (NH₄)₂Co(TeMo₂O₉)₂ was obtained through a conventional hydrothermal method. This compound was confirmed to crystallize in the monoclinic system of space group P2₁/c with a = 10.5133(5), b = 10.6456(5), c = 7.6078(5) Å, β = 108.879(6)º, V = 805.66(8) ų, Z = 2, M_r = 1021.97, D_c = 4.213 g/cm³, μ = 7.685 mm^–1, F(000) = 930, the final R = 0.0399 and wR = 0.1025 for 1580 observed reflections with I > 2σ(I), showing a tunnel structure with spin triangle-lattice composed by CoO₆ octahedra. Magnetic and heat capacity measurements confirmed a paramagnetic behavior down to 2 K with a negative Weiss temperature of –20 K, suggesting remarkable spin frustration in the system.