Strength deals with the durability of materials during usage and therefore is an important criterion for performance evaluation. Leather goods, which continue to be preferred by many over artificial substitutes, need to exhibit durable material performance. Strength testing, as related to an understanding of the endurance against force, is an important component of overall material behavior. Therefore, tensile testing should be well developed so as to analyze the properties of finished leathers and acquire realistic practical data. This study deals, in detail, with the evaluation of tensile properties considering the differences between engineering stress and true stress. In this examination of tensile behaviors three groups of garment leathers with different finishes (aniline, semi-aniline, and full pigmented finishes) were used. The samples were evaluated comparing engineering stress and true stress. In a Completely Randomized Design study, the statistical differences were calculated by the Duncan test in the level of P <= 0.05. Thereby, statistically significant differences between engineering stress and true stress between each of the three groups was verified.