Using a mixed-methods research design, this study explored the dominant causes, levels, and coping strategies of second language writing anxiety among 55 second-year Thai EFL undergraduate students majoring in English for International Communication. Data were collected from the Causes of Writing Anxiety Inventory (CWAI) questionnaire developed by Rezaei and Jafari (2014), the Second Language Writing Anxiety Inventory (SLWAI) developed by Cheng (2004), and a stimulated recall interview. Descriptive statistics were applied to analyze the data obtained from CWAI and SLWAI, while thematic analysis was used to identify themes from the stimulated recall interview. The results revealed that the predominant cause of writing anxiety was writing assignments, affecting 77.09% of students, followed by linguistic difficulties and fear of writing tests, each affecting 70.09%. Additionally, the study found that the level of writing anxiety among these students was high according to the writing anxiety questionnaire. Furthermore, during the stimulated recall interview, participants revealed five strategies typically used to manage their writing anxiety, namely positive self-talk, starting with a plan, relaxation techniques, goal setting, and seeking social support.