The bromination of 1-cyclopent-1-en-1-ylbenzene (4) in different solvents and at different temperatures was accompanied by the evolution of hydrogen bromide and yielded 1-(5-bromocyclopent-1-en-1-yl)benzene (8). Further bromination of 8 gave exclusively 2R(S),5R(S)-1-(1,2,5-tribromocyclopentyl) benzene (11). The experimental results were compared with the theoretical ones based on semi-empirical (MM+ and AM1), Hartree-Fock (HF) and density functional theory (DFT). The formation of 11 was explained by the formation of a weakly bridged bromoniun ion of type 9.