Student achievement in learning mathematics is considerably low in Indonesia. This study aims to discuss factors affecting learning achievements in mathematics in Indonesia, including direct and indirect influences, such as students' perception of teacher competence, learning anxiety, problem-solving ability, learning motivation, and mathematical connection ability. Quantitative approach and correlational method were used with a sample comprising 171 class XI students of Senior High School in Purworejo Regency, Central Java. The stratified cluster random sampling technique was used to determine the sample composition based on the National Examination scores for the 2018/2019 academic year. The results showed that four variables, except anxiety, significantly influence learning achievement. Furthermore, mathematical connection ability had the greatest direct impact on learning success at 0.38. Other indirect factors, such as influence through learning motivation and problem-solving ability, were at 0.140 and 0.133, respectively. These results are in line with previous studies which stated that mathematical connection ability is an important aspect in achieving student learning achievement. The ability to connect various materials studied with topics inside and outside mathematics has helped students understand the material to improve learning achievement. Furthermore, teachers can use these results as references in learning management by paying attention to various aspects, especially mathematical connection ability.