Given that students’ personality traits can have a powerful role in language learning, this study sought to investigate how well L2 leaners’ communication apprehension and request speech act can be predicted through the components of the Big Five Personality traits (extraversion, agreeableness, conscientiousness, neuroticism, and openness). The study also examined which of these traits could be the best predictor of L2 learners’ communication apprehension (CA) and request speech act. One hundred and seventy-nine Iranian EFL learners at three universities in Shiraz, Iran were recruited. To single out the participants for the study, Oxford Placement Test was employed. To identify the learners’ personality traits, gauge their pragmatic competence of request speech act, and measure their communication apprehension, The Big-Five Inventory, Discourse Completion Task, and the Personal Report of Communication Apprehension (PRCA-24) were applied, respectively. Standard multiple regression was used and the results showed that the Big Five personality can predict L2 learners’ communication apprehension and request speech act ability. Moreover, the results evidenced that extraversion and neuroticism largely contributed to L2 learners’ request speech act ability and CA, respectively. The findings offer implications for EFL teachers in helping their students increase their speech act productions and managing their communication apprehension based on their personality traits.