The effect of As content on the hot ductility of steel with 0.17 wt.% Cu was investigated at 700–1100 °C using a Gleeble- 3800 thermal–mechanical simulator. The results showed that increasing the As content from 0 to 0.15 wt.% obviously widened the hot ductility trough and pushed the trough into the high-temperature regime. Meanwhile, when the As content exceeded 0.10 wt.%, significant hot ductility deterioration was found. In the ferrite-austenite two-phase regions of 700–800 °C, the fracture appearance changed from dimple ductile to intergranular ductile or from intergranular ductile to intergranular decohesion with increasing As content. The inhibition formation of proeutectoid ferrite and austenite grain coarsening were responsible for the slight hot ductility deterioration by As in the two-phase region. In the austenite singlephase region above 850 °C, the fracture appearance changed from dimple ductile to intergranular decohesion with increasing As content, especially at 850–950 °C. Suppression of dynamic recrystallization and grain boundary segregation of As resulted in serious damage of the hot ductility and widened the ductility trough in the single-phase region.