The environmental stress cracking (ESC) of acrylonitrile-butadiene-styrene (ABS) copolymer caused by a non-ionic surfactant (poly-oxyethylene alkylether) was studied by constant-load tensile creep tests and edge crack tension (ECT) tests. The fracture surfaces were investigated by a scanning electron microscope (SEM) and the morphology of the crack tip was investigated by a transmission electron microscope (TEM). It was found that the results of the creep tests performed in the non-ionic surfactant were very different from those preformed in air. SEM images of the fracture surfaces shaved that there were three different mechanisms of fracture and that specimens had a tendency to rupture by ESC when the stress was small. The results of the ECT tests and the TEM images shaved that the change in the mechanism of the fracture was attributable to the change of morphology at the crack tip.