Laila, Affani. 2024. An Analysis of Grammatical Errors in Narrative Text Written by Grade 10th Students at SMAN 1 Sangatta Utara. Thesis. English Department, Faculty of Teacher Training and Education. Mulawarman University. Advisors: (1) Dr. Hasbi Sjamsir, M.Hum., (2) Dr. Weningtyas Parama Iswari, M.Ed. This research was about grammatical errors in students writing narrative text at the 10th grade of SMAN 1 Sangatta Utara. In this research, the researcher used quantitative descriptive method. This research is aimed to find out the most common types of grammatical errors based on Dulay et al., (1982) theory, the occurred of students’ grammatical errors in writing narrative text, and students’ factors that caused grammatical errors in writing narrative text. The data was collected by using accidentally selected participant. In this research, the researcher found that Misformation was the most common types of grammatical errors with 402 errors (60.36%). The occurred of students’ grammatical errors in writing narrative text because a lack of understanding of grammatical structures such as the used of verbs, tenses, spelling, and the used of capital letters, punctuation, and conjuction. As a whole, students still committed error in their writing and the teacher have to pay attention to the problem of the grammar structure.