We study the internal dynamics of the rich galaxy cluster ABGC 209 on the basis of new spectroscopic and photometric data. The distribution in redshift shows that ABCG 209 is a well isolated peak of 112 detected member galaxies at z=0.209, characterised by a high value of the line-of-sight velocity dispersion, {sigma}_v_=1250-1400km/s, on the whole observed area (1h^-1^Mpc from the cluster center), that leads to a virial mass of M=1.6-2.2x10^15^h^-1^M_{sun}_ within the virial radius, assuming the dynamical equilibrium. The data were collected at the ESO New Technology Telescope (NTT) with the ESO Multi Mode Instrument (EMMI) in October 2001.