This study analyzes Korean writing self-efficacy among third-year students at the University of Languages and International Studies – Vietnam National University, Hanoi, and examines the difficulties they encounter in completing writing tasks. The research adopts a mixed-methods approach, employing a questionnaire measuring three components (language conventions, ideation, and self-regulation) along with supplementary interviews. The results indicate that learners’ self-efficacy levels were moderate (2,92), with relatively higher confidence in language conventions but lower confidence in idea generation, particularly in vocabulary use and creativity. Regarding self-regulation, learners experienced difficulties in initiating writing tasks, maintaining concentration, and managing emotions during writing. Interview data further revealed that limited vocabulary, information overload, insufficient individualized feedback, and writing-related anxiety were the main contributing factors. The study proposes pedagogical directions aimed at enhancing Vietnamese learners’ writing self-efficacy.