Willingness to communicate (WTC) in English is specifically important because L2 (foreign/second language) communication is considered to be a key factor in L2 learning. When the opportunity to speak English arises, there are generally two options: speaking or avoiding it. Several factors might exert influence on the choice of either option by different individuals. In this vein, the current study investigated the underlying factors that lead to (un)willingness on the part of Iranian EFL (English as a Foreign Language) tertiary students. Through a purposive sampling procedure, this classroom-based case study recruited and examined 10 EFL learners in Iran over a period of three weeks. Data were collected employing semi-structured interviews, classroom observations and stimulated-recall interviews. Thematic analysis was performed to identify common themes from the participating students’ ideas. Results reveal that participants’ L2 WTC emerges as a result of the complex, dynamic and non-linear interaction between individual, contextual, and linguistic factors. These three factors interdependently exerted either facilitative or inhibitive impacts on an individual student’s WTC in class at any point in time. The current study, therefore, reinforces the need for teachers to be aware of the multiple factors which lead learners to be more or less willing to communicate in L2 classrooms.