New nitrosonium manganese(II) nitrate, (NO)Mn (NO ) , has been synthesized and structurally characterized. In the temperature range of 45-298 K, the crystal is hexagonal (centrosymmetric sp. gr. 6 / ). Mn ions are assembled into tubes along axis with both NO filling and coating. The nitrosonium cation is located in the framework cavity and is disordered by a 3-fold axis. At the temperature = 190 K, a structural phase transition related to the libration of the intertube NO group and a small variation of Mn polyhedron is observed. Moreover, the anomalies in physical properties of (NO)Mn (NO ) allow suggesting that ordering of NO units occurs at low temperatures. The antiferromagnetic ordering in this compound is preceded by the formation of a short-range correlation regime at about 25 K and takes place in two steps at = 12.0 K and = 8.4 K.