The Raman and infrared (IR) active lattice vibrations of xMn-concentration Bi2 − xMnxTe3 nanocrystals (NCs) as a dopant in semiconductor Bi2Te3 nanocrystals grown in a host glass matrix, whose symmetries correspond to the (Formula presented.) space group, are investigated by Raman scattering. Transmission electron microscopy images confirm the formation of Bi2 − xMnxTe3 nanocrystals with an average size of around 5.4 nm. The observation of the six hyperfine structure lines in electron paramagnetic resonance spectra confirms the incorporation of Mn2+ ions in Bi2Te3 nanocrystals. The vibrational modes of quintuple layer (QL) of the diluted magnetic semiconductor Bi2 − xMnxTe3 nanocrystals are modified in relation to pure Bi2Te3 nanocrystals. The appearance of the (Formula presented.) (95.5 cm−1), (Formula presented.) (114 cm−1), and (Formula presented.) (103 cm−1) IR-active modes is mainly due to quantum size effects. Indeed, the redshifts of the (Formula presented.) (95.5 cm−1), (Formula presented.) (103 cm−1), (Formula presented.) (110 cm−1), (Formula presented.) (114 cm−1), and (Formula presented.) (141 cm−1) vibrational modes give strong indications of the substitutional and interstitial incorporation of Mn2+ in the Bi2Te3 crystalline structure. In addition, the Raman spectra show the formation of Bi2OTe2 semiconductor due to the appearance of the (123 cm−1) mode. The investigation of the Bi2 − xMnxTe3 nanocrystal has promising potential to design new devices with magnetic and optical properties adjusted according to the xMn-concentration.