The construct of willingness to communicate (WTC) has attracted considerable attention from researchers worldwide, aiming to understand the reasons why certain learners avoid speaking while others actively choose to participate and initiate communication. Recognised as a key predictor of foreign language communication, WTC is considered essential for successful language learning, often seen as a crucial step preceding actual language use.

Substantial research has explored students' WTC in the face-to-face English foreign language classrooms. However, minimal research has examined WTC in an online context. This study aims to address this gap by investigating changing levels of students’ WTC during a naturalistic synchronous class by tracking students’ communication across several weeks using a self-rating instrument. It also aims to identify teacher-related factors that have influenced WTC rates among students, and to highlight teacher behaviours that are especially pertinent for promoting students' WTC in online classes.

A concurrent nested design was implemented in this study consisting of both qualitative and quantitative methods. Data was obtained using three methods: self-ratings of students’ in-class WTC, classroom observations, and semi-structured interviews with students following observation sessions during online classes. The same data collection procedure was repeated in four phases for two groups of learners with their teachers. Each group had 35 students where 8-9 students from each group completed self-ratings (N=17), and 4 students were interviewed (N=8).

 The findings revealed that three main aspects of teacher behaviour impact students’ WTC in online language classrooms: teacher affective behaviour, teacher pedagogical strategies, and teacher communication management. Among these three main categories, five teacher classroom strategies were found to be particularly significant for enhancing WTC in synchronous learning settings, namely: teacher verbal immediacy, modified input, authenticity, wait-time, and opportunities for breaks. This study offered conceptual and methodological contributions to the WTC literature and effective pedagogical implementations for language pedagogy.