With recent advancements in generative AI, the application of AI chatbots in language instruction has gained attention. Identifying the factors influencing, or related to the effectiveness and usefulness of AI-based solutions in language teaching is of special interest to the ELT community. This study aimed to investigate the relationship between EAP learners’ proficiency level, personality traits and final achievements in an AI-assisted academic writing course at Ilam University in Iran. To this end, a general proficiency test was given to 42 MA students enrolling in an academic writing course. Based on the test results, two homogeneous classes of 21 students with equal number of students of the three proficiency levels lower intermediate, upper intermediate and advanced were formed. Students received AI-assisted instruction using ChatGPT and Microsoft Copilot for outlining, revision guidance and feedback. Students were asked to complete NEO-PI-R inventory (short form) along with submission of three essays rated by three raters in a double-blind manner. The results of the data analysis revealed that more proficient students achieved higher, and the traits conscientiousness, extraversion and openness to experience had direct positive relationship with achievement, while neuroticism had direct negative relationship, and no significant relationship was observed between agreeableness and achievement.
