The tearing resistance of the two principal strata of leather (the grain and the cerium layers) has been assessed via the measurement of tearing energy and notch sensitivity. Observations of the distribution of strain around notches and the form of the tear tips are also reported. It was found that the grain layer had only 20% of the tearing energy possessed by the cerium. In addition, the strength of the grain was considerably more sensitive to the presence of sharp notches. It is suggested that these differences in strength between the two strata of leather are associated with the greater ability of the corium layer’s fibre structure to impede propagating tears by means of tear tip blunting and fibre pull out.