The learning modality has been greatly affected due to the COVID-19 pandemic, which has resulted in switching from offline learning to online learning. While much research has investigated factors affecting students' online language learning engagement, a few studies have examined the EFL students' discernment of psychological factors. Therefore, this study adopted a quantitative design for data collection and analysis to scrutinize the psychological factors affecting EFL students' online learning engagement. A group of 174 EFL students conveniently chosen from three universities in Vietnam partook in answering a questionnaire whose data were quantitatively processed by the SPSS software. Three remarkable psychological factors, namely relaxation, self-confidence, and anxiety, were found to affect EFL students' online language learning engagement at a high level, whereas motivation, satisfaction, enjoyment, and interest moderately impacted their online language learning engagement. Additionally, anxiety was found to have no correlation with satisfaction but had negative correlations with other factors. Meanwhile, enjoyment, relaxation, interest, motivation, self-confidence, and satisfaction were positively correlated with one another from strong to modest levels. This study suggests some recommendations in an attempt to enhance the quality of online learning modality in the research contexts and other similar ones.