This study aims to determine the relationship between emotional maturity and aggressive behavior. This study uses correlational quantitative methods and data collection techniques using a scale. The population in this study were all students of class XII of SMA Muhammadiyah Kota Pagar Alam, totaling 202 people, while the sample amounted to 127 people. The sampling technique used in this research is cluster random sampling. The hypothesis in this study is that there is a relationship between emotional maturity and aggressive behavior in class XII students of SMA Muhammadiyah Kota Pagar Alam. The measuring instrument used in this study uses two scales, namely the emotional maturity scales according to Walgito (2004) and the aggressive behavior scale according to Bush and Perry (1992). The data obtained in this study were analyzed using the Pearson’s Product Moment analysis technique which was used to see the relationship between variables with the help of SPSS version 26.0 for windows. Based on the results of the research that has been done, it can be concluded that there is a significant negative relationship between emotional matury and aggressive behavior, this is evidenced by the results of correlation coefficient which shows the number r= -0,514 with a sig value. 0,000 where p