During the COVID-19 pandemic, in which social distancing has become the norm, blended online learning, which consists of two main components: namely synchronous online instruction through a virtual conferencing platform, or live virtual classroom (LVC), and asynchronous online learning through a learning management system (LMS), has largely replaced face-to-face classrooms. After 2,217 EFL freshmen and 16 EFL teachers at a public university in Thailand participated in blended online learning instruction in a foundation English course in the first semester of academic year 2021, their perceptions and experiences regarding the instruction were investigated using online questionnaires and semi-structured interviews. An explanatory sequential mixed methods design was employed to obtain empirical information from the participants. The findings obtained from the questionnaires (590 voluntary students and 12 voluntary teachers) and semi-structured interviews (15 voluntary students and 5 voluntary teachers) indicated that blended online learning was appropriate and beneficial in EFL classes for the undergraduate students and could support the social distancing measures put in place due to COVID-19. While there are some limitations, inconveniences, and challenges related to blended online learning, it has been demonstrated to be effective in improving students' English ability while saving time and expense by eliminating the need for travel to the university and providing flexibility regarding the time and place of learning and teaching. Implications and recommendations for blended online learning and its two main components were also concluded from the findings and are discussed in the study.