Improving conceptual knowledge in mathematics can be achieved through various strategies such as active learning, visual aids, real-world applications, frequent assessment and feedback, encouraging metacognition, scaffolded instruction, collaborative learning, and the use of technology. This study examined the conceptual knowledge and error analysis among pre-service teachers in Mathematics. It aimed to determine their level of conceptual knowledge, identify common errors, and explore the relationship between their understanding and errors. Using a descriptive correlational research design, data were collected from all pre-service teachers present and analyzed using frequency counts, percentages, and Pearson correlation. The findings revealed a moderate level of conceptual knowledge among the pre-service teachers, with common errors in various mathematical topics. A significant relationship was found between their conceptual knowledge and the errors committed. The study concludes that enhancing conceptual knowledge is crucial for reducing errors and recommends targeted interventions and continuous professional development for pre-service teachers. These findings provide valuable insights for education researchers and practitioners, particularly in ASEAN Teacher Education, to address current trends, problems, and challenges in the field.