Delamination is one of the most common failure types among polymer composites, which occurs in all types of loading, including mode I. For this reason, composite laminates are used in different ways, including the method of using metal Z-pins along the thickness, in order to delay the Delamination time and increase the strain energy release rate. In the present study, the mechanical performance and Acoustic Emission of Delamination in glass/polyester composite have been investigated using the ASTM D5528-01 standard in the manufacture of DCB samples. First, the force-displacement curve and crack growth resulting from Delamination for Z-pinned steel and copper samples were compared with those without pins. The critical load of each sample to obtain the interlayer fracture toughness for mechanical behavior according to the standard D5528-01, as well as the critical load for the Acoustic Emission behavior, was associated with the increase and growth of some signal energy and the jump of cumulative Acoustic Emission energy. It was found that the strain energy release rate increases by using metal pins along the thickness. Also, the fracture toughness obtained from the mechanical method was verified by the Acoustic Emission method.