The study of the Mandarin language in Indonesia is developing rapidly, yet structural differences in grammar often pose difficulties for novice learners, particularly in differentiating the modal verbs 可以 (kěyǐ), 能 (néng), and 会 (huì), all of which share the similar meaning of "can" or "be able to". This study aims to describe the forms of errors in using these modal verbs and to identify the most dominant type of error made by students. The research method employed is descriptive quantitative. The research subjects consisted of 16 second-semester students from the Mandarin Language Education Study Program at Universitas Kristen Indonesia for the 2025/2026 Academic Year. Data were collected through a Google Form-based test consisting of 15 multiple-choice questions, 10 fill-in-the-blank questions, and an essay test for sentence construction. Data analysis was performed by calculating error frequencies and percentages. The results revealed three main forms of errors: the confusion between 能 (néng) and 可以 (kěyǐ), 能 (néng) and 会 (huì), and 可以 (kěyǐ) and 会 (huì). Among these, the modal verb 能 (néng) consistently emerged as the most dominant source of error made by students, with error rates reaching 81.25% in the multiple-choice section, 68.75% in the fill-in-the-blank section, and 18.75% in the essay test. These errors are categorized as systematic errors due to a lack of conceptual understanding regarding the situational application of 能 (néng). This research is expected to provide constructive feedback for educators in designing more effective learning strategies.