Vegetable tanned leather is very sensitive to environmentalfactors, especially acidic pollutants. In addition to environmentalfactors, the type of animal and tannin consumed highlyinfluences the structure and deterioration of leather. Therefore,this comparative study aimed at evaluating the stability of sheepand goat leather, tanned with mimosa extract, during theaccelerated aging process. The leathers were submitted toaccelerated aging for two weeks at 40°C, 50% RH and 100 ppmSO2 concentration. The attenuated total reflectance Fouriertransform infrared (ATR-FTIR) spectroscopy, colorimetry,fiber-optics reflectance spectroscopy (FORS), pH measurements,investigation of mechanical properties and shrinkagetemperature (Ts) were used to investigate influence of theaccelerated aging condition on physical and chemical propertiesof leather. Results showed that sheep leather has better structuralstability against acidic deterioration with compared to goatleather. While, goat leather showed higher color stability thansheep leather. Moreover, results revealed that deterioration levelin grain layer was more severe than corium.