The vibrations of o-, m- and p-bromofluorobenzene (BrFPh) in the first electronically excited state are studied by (1?+?1) resonance-enhanced two-photon ionization spectroscopy. The observed vibrational bands have been assigned on the basis of comparison with the results from theoretical calculations. The band origins of the S₁?←?S₀ electronic transitions of o-, m- and p-BrFPh, which were influenced by positive resonance effect and negative inductive effect, are found to be 36986.68?cm^?1, 36961.48?cm^?1 and 36223.20?cm^?1 respectively. Meanwhile, the potential barrier height (the energy of the crossing points between the bound S₁ state and a repulsive state relative to the S₁ minimum) of p-BrFPh is determined to be lower than 2815?cm^?1 (0.3490?eV) by the REMPI spectra of bromine atom and p-BrFPh molecule.