The COVID-19 pandemic has forced universities to make a radical switch from face-to-face traditional teaching (TT) to completely online learning (OL). Thus, many studies proposed the proper OL environment for a specific subject and evaluated its effectiveness. However, few studies have empirically compared the proposed OL environment with TT to determine which has better learning effectiveness. More importantly, an OL environment and the self-regulated learning (SRL) ability of a student interactively influence the student's learning effectiveness. However, few studies have investigated how an OL environment influences the learning behaviours of the students with different SRL abilities. Thus, the aims of this study were to compare the adopted hybrid OL environment with TT and examine how the hybrid OL environment individually influences students with different SRL levels. This study has three significant findings. First, students have better participation rate and work quality in the OL than in TT. Second, the high-SRL and middle-SRL students have higher work quality under the OL than under TT, while the middle-SRL and low-SRL students have higher participation rates under the OL than under TT. Third, while students overall do not particularly favour OL or TT, the middle-SRL students particularly prefer OL.