Leather materials are subjected to various deformation states during their elaboration and their use as a final product. Although the mechanical response of leathers under tension has been studied in the literature for decades, scarce information is available on the nature of their elasticity and more generally on their thermomechanical behavior. In the present study, four leathers were tested under uniaxial loading conditions while temperature changes were measured at the specimen surface using infrared thermography. Two types of tests were performed at constant ambient temperature: monotonous displacement-controlled tests until failure and cyclic load-unload tests with increasing amplitudes. The heat sources at the origin of the temperature changes were also determined by using a version of the heat diffusion equation applicable to homogeneous tests. Results enabled us to discuss the nature of thermoelastic couplings in leathers. Intrinsic dissipation caused by mechanical irreversibility was also detected and quantified. Distinct responses are evidenced depending on the type of leather tested.