The effect of drying temperature on the morphology and mechanical properties of acrylic fibers was studied. It was found that the porous fiber was contracted in both the axial and radial directions during drying, and internal microvoids between fibrils within fiber were eliminated. This pheno-menon has frequently been termed collapse. The collapsed fiber was lustrous and transparent. The degree of crystallinty and crystallite size of dried fiber increased with increasing drying temperature and the fiber structure apparently became denser and more homogeneous. On the other hand, the mechanical properties of drawn fibers were discussed in relation to the morphology of tensile failure. The fibers dried at room temperature or 70˚C, which contained many flaws due to the trace of voids, exhibited tensile fracture with axial splits, whereas the collapsed fiber dried at 130˚C exhibited tensile failure perpendicular to the fiber axis. These morphological difference in tensile failure resulted in a difference in mechanical properties. The higher mechanical properties of the collapsed fiber might be attributed to an increase in the degree of bonding between fibrils.