Content Knowledge (CK) and Pedagogical Content Knowledge (PCK) are factors that influence pre-service teachers’ teaching practices. This research aims to (1) identify the foundational knowledge of pre-service teachers regarding mathematical content knowledge and pedagogical content knowledge, (2) determine their level of confidence in teaching mathematical content at the lower secondary level, and (3) analyze the influence of their mathematics scores on their confidence in teaching mathematics. Employing quantitative approach this study utilizes test questionnaires and confidence-related questionnaires in teaching to collect data. The collected data from pre-service teachers at four regional teacher training centers, including those in Kampong Cham, Takeo, Prey Veng, and Kandal provinces were analyzed descriptive and regression analysis. The results of the analysis indicate that pre-service teachers currently have low levels of content knowledge, and their confidence in teaching is at a moderate level. Content Knowledge (CK) has a significant influence on Pedagogical Content Knowledge (PCK). Furthermore, Pedagogical Content Knowledge has a significant effect on teaching confidence. However, Content Knowledge does not directly affect their confidence in teaching. This research suggests that instructors should place more emphasis on teaching PCK and CK at the secondary school level and provide pre-service teachers with ample opportunities for teaching practice.