Deformation mechanisms in a high thermal resistant poly(acrylonitrile-butadiene-styrene) (ABS) were investigated using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The work followed our previous study, in which TEM was used for the craze observation and SAXS for the shear yielding, to evaluate the relationship between the mechanical properties and the deformation mechanisms of the ABS under static tension and Izod impact, The current results support our previous conclusion that the combination of TEM and SAXS enables us to identify the deformation mechanisms in the ABS, and provide new evidence for the coexistence of crazing and shear yielding. The SAXS patterns suggest that shear yielding occurred in the ABS, even under the impact loading. We concluded from the study that the occurrence of shear yielding had a major effect on the toughness enhancement of the ABS.