This study discussed the correlation between students’ motivation and their grammar achievement at English Department of Halu Oleo University. The objective of this study is to find out the correlation between students’ motivation in learning grammar and their grammar achievement at English Department of Halu Oleo University. The sample of this study is class A of 2021 who programmed Basic Grammar Course. In collecting the data, this study was distributing questionnaires and collected students’ basic grammar scores from their lecturer. In analyzing the data, the questionnaires were assessed by Likert’s scale rating then conducted correlational research in SPSS 16. The result of this study shows that there is medium positive correlation between students’ motivation in learning grammar and their basic grammar achievement. It is proved by the pearson correlation is 0.458 and categorized as a medium correlation. Although students’ motivation and their basic grammar achievement correlate each other, the contribution of students’ motivation to students’ basic grammar achievement is only 20% and 80% is from other factors that are not examined in this study. After testing the hypothesis, it is found that H1 is accepted which means that there is significant correlation between students’ motivation and their basic grammar achievement. In conclusion, there is a medium positive correlation between students’ motivation in learning grammar and their grammar achievement at English Department of Halu Oleo University.