This work deals, for the first time, with the modeling of absolute line intensities in the fundamental 2 and 5 bands of CH379Br and CH381Br at 7 µm. For that, four unapodized absorption spectra of CH3Br (natural abundance, 99% purity, P×L = 0.082-0.165 atm×cm, room temperature) were measured in the range 1260-1560 cm-1, at a resolution of 0.002 cm-1 using a Fourier transform spectrometer Bruker IFS 120 HR. For both isotopomers, 313 line intensities were analyzed within the dyad system required to account properly for the strong Coriolis coupling between 2 and 5. The intensity fit of experimental data led to the determination of the dipole moment derivatives and relative to the 2 and 5 bands, as well as the first-order Herman-Wallis correction in to . The observed line intensities are fitted to 3.0% (3.3%) for 2 at 1309.9 cm-1 and 2.6% (3.0%) for 5 at 1442.9 cm-1, respectively for CH379Br and CH381Br. The values derived for the vibrational band strengths of 2 and 5 are 55.7(0.6) and 39.2(0.3) cm-2.atm-1 at 296 K, respectively. The corresponding assignments and line positions of the dyad from previous work [F. Kwabia Tchana et al., J. Mol. Spectrosc., 228 441, (2004)] are combined with the present intensity study to provide an improved CH3Br database for atmospheric applications.