Adjective order is one part of grammar lesson that is taught in senior high school. In improving students' understanding of adjective order, one technique that can be used in the learning process is the mistake buster. The objective of this study is to figure out that the mistake-buster technique is appropriate to improve students' understanding of adjective order. This study used a quantitative method with a quasi-experimental. The sample consisted of 28 students in class XI IPA 1, with the total population consisting of all class XI in MAN 3 Bireuen. Data collection was done through the application of pre-post tests. In processing data, this study used spss 26.0. The results of this study indicated that the utilization of the mistake-buster method has an impact on improving students' understanding of adjective order. This is evidenced by students’ scores that change quite significantly. The students' pre-test mean score was 37.89 with a standard deviation of 15.0538, and their post-test mean score was 76.29 with a standard deviation of 11.02138. The researcher observed that the degrees of freedom were 27, and the probability value was less than α (0.00 ˂ 0.05). It can be concluded that the null hypothesis (H0) is rejected, and the alternative hypothesis (Ha) is accepted, which means that the mistake buster is efficacious in improving students' understanding of adjective order.