This research aims to identify interactional patterns in the ESP online teaching mode of the fifth semester of the English Department at Universitas Negeri Medan. This research applies descriptive quantitative methodology and focuses on class A of the English Department's fifth semester, which consisted of 36 students and one lecturer who taught online utilizing Google Meet as the platform. This study's data consisted of three audiovisual recordings made by the lecturer. The data were recognized using the IRF pattern of interaction identification table and analyzed using the IRF model. The first discovery revealed that the most frequently used pattern by the lecturer is IRF as a full pattern, followed by IR as a semi-complete pattern and IF as an incomplete pattern. The second finding revealed that elicitation occurs more frequently in classroom interactions. It is possible to infer that this classroom had a high level of interaction since the lecturer provided equal opportunities for students to begin the conversation, resulting in active student participation.