Chemical composition dependent vibrational modes of manganese-based bismuth telluride (MBT) magnetic topological insulators thin films grown by molecular beam epitaxy were studied by Raman spectroscopy and compared with the vibrational modes of Bi2Te3 films. Intensity of (Formula presented.) TO mode was much stronger in Bi efficient MBT film. In contrast, vibrational cross-section of (Formula presented.) LO mode was stronger in Bi deficient MBT compound. (Formula presented.) TO mode corresponds to in-plane vibrations of Bi-Te atomic layers. Deficiency of Bi atoms in the MBT indicated that the vibrational degree of freedom of Bi-Te in the septuple unit cell was less probable. Antisymmetric out-of-phase vibration of Te-Te atoms resulted in (Formula presented.) LO mode in which Bi atom was stationary, therefore vibrational cross-section of this mode for Bi deficient MBT film was stronger. A resonantly excited Eg and A1g modes was observed at excitation energy 1.57 eV associated to deformation potential and Frohlich electron–phonon coupling, respectively.