• MgTa 2 S 5 is revealed to be a BCS superconductor with T c = 1 K, and with a superconducting energy gap of 0.25 meV. • It is the newest member of the AM 2 S 5 compounds, A = alkaline earth metal, M = transition metal. • The electronic specific heat coefficient 11.1 mJ/mole K 2 is reported. Superconductivity in the new compound, MgTa 2 S 5 , is reported. Its crystal structure was indexed to space group C 2 / m , which is monoclinic with lattice parameters a = 5.784(5) Å, b = 12.680(3) Å, and c = 6.106(5) Å, with β = 112.64 ∘ . Electrical resistivity reveals metallic behavior with ρ (296 K) = 5.2 m Ω cm and bulk superconductivity below T c = 1 K. Measurements of the specific heat C reveal the electronic specific heat coefficient γ = 11.1(5) mJ/mol K 2 , a jump in C at T c illustrating bulk superconductivity, and an energy gap associated with the superconducting state of E g = 0.25(3) meV. MgTa 2 S 5 can be classified as a BCS superconductor. An unidentified minority phase present in the sample ( ∼ 4%) exhibits a superconducting phase transition near 2.6 K.