A reinforced trouser tear test was developed to evaluate the tear resistance of thin ductile films. Tests with blown film of linear low-density polyethylene blended with up to 30 wt% of a high melt strength polypropylene (hmsPP) demonstrated that the test differentiated among films based on composition and thickness. Increasing the amount of hmsPP in the film decreased the tear resistance. Also, thinner films were less tear-resistant than thicker films. Stable crack growth occurred with transformation of a crack tip damage zone into a continuous yielded zone at the fractured edge. The tear energy was directly proportional to the width of the yielded zone. Correspondence between the energy to deform the material in the yielded zone and the measured tear energy demonstrated that yielding in the vicinity of the propagating crack provided the resistance to tearing in these films.