Abstract ESR measurements on Mn(II) ion doped in single crystals of Cd(NH3)2Ni(CN)4·2C6H6 confirmed the structure of the Hofmann-type clathrate predicted before. Spin Hamiltonian parameters obtained are g=2.0033±0.0010, A=(−84.9±1.0)×10−4 cm−1 (123 K) and (−84.3±1.0)×10−4 cm−1 (room temp), D=(67.5±1.0)×10−4 cm−1 (123 K) and (17.3±1.0)×10−4 cm−1 (room temp), and a=(16.5±1.0)×10−4 cm−1. The environment of Mn(II) ion has a tetragonally distorted cubic symmetry. While the parameter a is independent of temperature, the parameter D is found to be dependent on temperature obeying to D∝(T0–T)2 where T0 is 473 K. The nuclear forbidden lines, Δm=±1, were also detected, intensities of which vary in terms of D squared.