Concentration is one of the most important aspects determining second language learners' success and performance during language learning. As a result, it has garnered significant attention from teachers and researchers. The recent worldwide health crisis has sparked revolutionary reforms in education, both in schools and universities. Universities and schools are required to conduct online English teaching; this practice has been ingrained in the educational sector and continues to this day. Concentration in online learning is becoming an increasingly important issue. A qualitative descriptive study investigated students' opinions of online instruction and how it affects their focus. Semi-structured interviews were conducted with 30 students from complete classes, 12 male and 18 female. According to the data in this research, the researchers found two main factors influencing the students' concentration in online learning. Those two factors include internal factors; (1) Students' Understanding Ability (2) Students' Interest (3) Students' Physical Aspect and external factors; (1) a Large Volume of Teaching Material in a Session, (2) Teachers' Teaching Method, (3) Lack of Contact and Engagement between Teacher and Student, (4) Digital Technology Devices, (5) Learning Environment.
Key words: Concentration, English Learning, Online Learning