<p>This mixed-methods study investigated the relationship between the Big Five personality traits and Willingness to Communicate (WTC) in English among Iranian EFL learners. A total of 100 intermediate-level students completed the Big Five Personality Traits Scale and an L2 WTC Scale, with 15 participants selected for semi-structured interviews to provide deeper insights. Quantitative analysis revealed that neuroticism was negatively correlated with L2 WTC (<i>r</i> = -.486, <i>p</i> &lt; .001), while extraversion (<i>r</i> = .432, <i>p</i> &lt; .001), openness (<i>r</i> = .381, <i>p</i> &lt; .001), and agreeableness (<i>r</i> = .291, <i>p</i> &lt; .05) showed positive relationships. Bayesian regression modeling, chosen for its ability to handle model uncertainty and provide probabilistic estimates, identified neuroticism, extraversion, and openness as key predictors, with neuroticism exerting the strongest negative influence. Together, these traits explained 32.1% of the variance in WTC. The qualitative findings complemented the quantitative results by exploring participants’ perceptions. Thematic analysis highlighted three key themes: emotional responses to L2 communication, personality-driven communication strategies, and the influence of supportive classroom environments. Classrooms characterized by positive teacher feedback, peer encouragement, and low anxiety were found to enhance WTC, especially for learners high in neuroticism. These findings underscore the interplay between individual differences and contextual factors in shaping L2 communication, offering practical implications for language pedagogy and learner-centered strategies.</p>