[Mn(5-ATZ)2Cl2]n (1) (5-ATZ - 5-amino-1-H-tetrazole) was synthesized from the reaction of 5-ATZ and manganese(II) chloride and isolated by solution evaporation at room temperature. 1 was characterized by elemental analysis, X-ray crystallography, infrared and EPR spectroscopy as well as magnetic measurements. In the crystal structure, [Mn(5-ATZ)2Cl2] units are linked by double μ2-bridging chlorides to form 1-D chains parallel to the a-axis. The Mn sphere approximates to octahedral with the metal coordinated by four chlorides in the equatorial plane and two 5-ATZ molecules, bound through their ring nitrogens, in axial positions. The intramolecular N-H···Cl hydrogen bond between the 5-ATZ amino group and the adjacent coordinated Cl- stabilizes the chain. N-H···N hydrogen bonds between adjacent chains form a 3D supramolecular framework. No hyperfine coupling to the Mn nuclei (I = 5/2) is observed in the powdered EPR spectrum of 1 at 77 K. The frozen solution EPR spectrum provides evidence of the mononuclearity of 1 in methanol. The magnetic properties have been analyzed using the Hamiltonian H = -J∑Si · Si+1 with J = −1.38(3) cm−1 and g = 2.00(1). A small value of the exchange parameter is typical for 1-D six-coordinate bis(μ2-chloro) Mn(II) polymers.