This article reports a critical appraisal of the factors affecting fibrillation behavior (axial splitting tendency) of uniaxially oriented tapes prepared from high-density polyethylene and its blends. The drawn tapes were characterized by combined tension-twist fibrillation test, a new test proposed for this work. In addition, the drawn tapes were also characterized for microstructural details such as amorphous phase orientation, degree of crystallinity, void characteristics, and fracture surface morphology. It was found that an increase in amorphous phase orientation and degree of crystallinity systematically decreases the fibrillation strength and fibrillation toughness of tapes. General structural models to explain this phenomenon via microcrack formation, interfibrillar shearing process, and failure are proposed.