The study focuses on applying Error Analysis (EA) to improve academic Vietnamese writing skills for international students. From a survey of 120 writings by 85 students from five countries, the authors recorded 487 errors in four main groups: grammar (38.81%), vocabulary (29.16%), syntax (19.92%), and academic style (12.11%). The main cause was language transfer from the mother tongue (53.8%), followed by intralingual errors such as overgeneralization and simplification (28.34%), and a lack of academic knowledge or avoidance strategies (17.86%). The results indicate that errors are not random phenomena but systematic, reflecting the formation of learners’ “interlanguage.” On this basis, the study proposes teaching solutions: strengthening practice on nouns–classifiers and word order, expanding academic vocabulary, training text organization skills and objective style, while using feedback based on error analysis. For educational institutions, the study recommends developing a database of typical errors and supplementary academic writing courses integrating language–thinking–culture