This thesis aims to describe the grammatical errors in writing argumentative paragraphs by the English Department students’ at Lambung Mangkurat University Banjarmasin Batch 2016. The instrument is written test. The written test was distributed to 60 students who took Academic Writing. There were 3 topics given in the test. And the methodology used in this research was descriptive. Moreover, the approach of this research was quantitative.

Research findings showed that the students of Academic Writing class made grammatical errors in writing argumentative paragraph. The errors cover from factual errors, typographical errors and punctuation errors. The highest of errors occurant in students’ writing is on factual of errors, while the lowest of errors occurant on punctuation errors. The result is consistent from the first test up to the last test.

In conclusion, all errors comes from the students. It is suggested that the teachers should try the students’ skill in grammatical writing argumentative paragraph by giving more exercises on writing especially grammar, that can minimize students’ difficulties in grammatical writing argumentative paragraph.