In this study, it is aimed to investigate the relationship between the beliefs and attitudes of the secondary school students towards geometry and their mathematical achievements. The extent to which the belief and attitude towards geometry predicts mathematics achievement is another subject. The study was designed with a quantitative method, survey method. Research, located on Turkey's Mediterranean Coast from secondary schools in the province chosen by simple random sampling medium sized secondary school in 2019-2020 academic year studying 490 (255 boys and girls 235) was carried out by secondary school students. As a data collection tool, "Personal Information Form", "Geometry Belief Scale" and "Geometry Attitude Scale" were applied to secondary school students. Data were analyzed using t-test, ANOVA, Cohen's f and Cohen's d effect size values, correlation and multiple regression analysis methods. As a result of the data analysis, a significant positive relationship was found between the geometry beliefs and attitudes of secondary school students and mathematics achievement. In addition, geometry beliefs and attitudes were found to be significant predictors of mathematics achievement.