This research evaluated the beam-to-column connection classification index recommended by Eurocode 3 Part 1.8 and ANSI/AISC 360-10 specifications. A test programme was considered to examine the moment-rotation (M-θ) curve of semi-and fully rigid connections with variable parameters. The maximum moment capacity and initial elastic stiffness of the connections were the main parameters resulting from the M-θ curve. The performance of beams with semi-rigid connections was also evaluated through a classical method. The results clearly showed that the Eurocode 3 specification provides a more reliable classification index for the investigated connections. By evaluating the data of this research, a new classification system based on the rigidity, ultimate strength level, and ductility requirements was proposed. The results of this research provide an important contribution to the existing literature as the actual responses of beam-to-column connections are semi-rigid, and therefore such behaviour should be included in the analysis and design method.