Leather artifacts in El-Azhar El-Sharief Library suffer from deterioration. Some aspects of deterioration are found on these artifacts such as darkness, missed parts, insect holes, etc. These are due to the effect of some factors (physical, chemical, biological, and human factors. This study aims to evaluate the condition of a leather binding, explain the aspects and mechanism of its deterioration, and prepare for laying a plan for applying the appropriate conservation techniques. The analytical techniques used were visual assessment, digital microscope, investigation of the surface morphology by scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), pH value, and isolation and identification of fungi. The digital light microscope revealed that the surface became coarse, and advanced erosion was also noticed. SEM revealed the weakness of the fiber structures of leather, and holes caused by insects were also noticed. FTIR analysis proved that there was a change in the chemical composition of historical leather. The identified fungi were Aspergillus sp. Ah55. pH measurement stated that the pH of leather binding decreased significantly under the effect of acidic conditions in the surrounding environment conditions. This study recommends the necessity of carrying out conservation treatment processes for the leather binding studied including cleaning, consolidation, disinfection, completion of missed parts, etc. Preventive conservation should be also taken into consideration.