Low temperature X-irradiation of single Ph₃GeBr produces a radical whose unpaired electron is mainly localized on the Germanium (~80%) and the Bromine atom (~20%). At first sight three identifications can be proposed for this radiation damage: Ph₃GeBr⁺, Ph₂GeBr and Ph₃GeBr^-. The analysis of the ⁷³Ge, ⁸¹Br magnetic and ⁸¹Br quadrupole hyperfine tensors indicates that the radical anion is the most probable species. The mutual orientation of the bromine and germanium magnetic hyperfine interaction shows that Ph₃GeBr^- adopts a distorted pyramidal structure intermediate between the C₃-conformation reported for Ph₃PCl and the trigonal bipyramid reported for PF_4.