We report measurements of the magnetic properties of the molecular magnet NH4Ni(mnt)2.H2O. The magnetic exchange in this salt is ferromagnetic below 100K, with a Weiss constant of 7 K. Long range magnetic ordering is observed below 5 K. Single crystals of this salt have been studied down to 2 K in a SQUID magnetometer. The salt is found to have hard and easy magnetisation directions. Magnetisation of 1800 emuG/mol at 2 kOe was measured at 2 K for magnetic fields applied perpendicular to the molecular stacking axis.