Abstract: Damage to paper (sulfate pulp, cotton half-stuff, and flax half-stuff) caused by the Aspergillus niger, A. sclerotiorum, and Penicillium chrysogenum fungi is investigated by Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. It is shown that the use of application infrared Fourier-transform absorption spectroscopy allows one to identify the initial stages of damage from a decrease in the degree of crystallinity of the cellulose contained in paper. The absorption band near 900 cm ^–1 is used as an indicator of early stages of damage. An increase in the amide II peak at 1550 cm ^–1 and spectral changes in the region of valence vibrations of the C–H bonds (2800–3000 cm ^–1) are observed in the case of heavier damage. The obtained data indicate that the vibrational spectroscopy techniques are promising in the study of damage of archive documents.