Effective written communication is not only a crucial skill for academic achievement but also for business context as it could lead to individual professional career success and profitable accomplishment. To achieve these goals requires concise and correct communication. This study, therefore, aims to explore the most frequently-made errors by 30 Business English major students. From the total number of 14,118 words, the study found that the students most frequently made three types of errors: morphological (17.91%), syntactical (45.37%), and mechanical (36.72%) levels. Of all the errors that occurred, article errors appeared to be the most problematic use (17.31%), followed by punctuation (13.34%), plurality (13.43%), capitalization (9.55%), and preposition (8.96%) errors. The findings suggested that mostly-made errors by the Business English major students were influenced by the interference of their first language. Additionally, apart from explicit grammar teaching, greater exposure to the target language is also required in the classroom.