The numerical model of the double-sided extended end-plate composite joint presented in Part I of this paper is used to evaluate the seismic performance of this joint when used in moment-resisting frames. For this purpose, three frames of different heights and spans were designed and analysed. Two pushover analyses, with uniform and modal lateral load, were performed to evaluate the ultimate capacity of the frame. Incremental dynamic analyses (IDAs) were also performed to evaluate the seismic properties of each frame using accelerograms that match three types of elastic response spectra. The data provided by the simulations has allowed us to obtain the behaviour factors of the composite frames that use this type of joint, and to ensure their improved behaviour under seismic actions.