Students’ engagement is a significant predictor of the students’ academic achievement. The objective of this research found out the correlation between students’ engagement and their English academic achievement. This research was conducted at SMAN 8 Semarang with the total of 223 as the population. The sampling technique was simple random sampling and it was found 143 students. The researcher took some 11th grade students as the trial sample to measure validity and reliability of research instrument. In collecting the data, the researcher distributed the questionnaire to explore the relationship between two variables, students engagement and their English academic achievement. This correlational research used quantitative approach which used descriptive statistics, normality test, and correlation test. Correlation Pearson Test was used to analyse the data and the hypothesis testing was computed using SPSS version 26.0. After giving instrument to trial sample, the researcher analysed the data, it was found that reliability of students engagement was 0.759. It means that students engagement instrument was reliable. After calculating the data, the researcher found the research findings that 11th grade students have positive and good engagement which involves aspects of teaching learning cycle including learning activity with the highest result of “agree” option totalling 921. Meanwhile, the next finding is to answer the research problem. The significance correlation was 0.000. The value of significance correlation was <0.05. It meant that students engagement and their English academic achievement have a strong significant correlation. The research’s result can be interpreted that there was significant correlation between students engagement and their English academic achievement.