The effect of reinforcing agent type and composition on the fracture behavior of short glass fiber (SGF), CaCO3 particle, and glass fiber/CaCO3 hybrid reinforced ABS/PA6 blend based composites have been studied by using the essential work of fracture (EWF) method. Two millimeter thick rectangular shaped samples were first processed in twin-screw extruder and they were subsequently injection molded. Double edge notched tensile (DENT) specimens with various ligament lengths were subjected to tensile tests at 2 mm/min constant deformation rate at room temperature in order to determine EWF parameters. For the neat matrix and 10 wt% calcite reinforced materials fractured in ductile manner, that is, the ligament fully yielded and the crack stably propagated unlike the other compositions. For the neat matrix, both the specific EWF, we, and the nonessential work of fracture, βwp, values dramatically decreased with increasing reinforcement weight ratio regardless of the agent type. The analyzing of yielding and necking/tearing components of essential and nonessential parameters showed that for the samples reinforced with SGF we,nt > we,y and βntwp,nt > βywp,y, indicating that a majority of fracture energy was dissipated in the necking and tearing stages of fracture process. POLYM. ENG. SCI., 54:540–550, 2014. © 2013 Society of Plastics Engineers