This thesis entitled, “Determinants of Numeracy in Mathematics Competency and Skills Development,” was conducted to determine the relationship between numeracy skills and mathematics competency and mathematical skills development. Specifically, it aimed to identify the level of key determinants of numeracy, learners’ competence, and learners’ mathematical skills development. It also measured the relationship between the determinants of numeracy skills and mathematics competence, as well as the relationship between the determinants of numeracy skills and mathematical skills. Descriptive method of the research is used to be able to observe a large mass of target population and make required conclusions about the variables. The primary respondents are the selected one hundred seventy-six Grade 11 – students of Nicolas L. Galvez Memorial Integrated National High School, Bay, Laguna, S.Y. 2023-2024. The level of determinants of numeracy skills in terms of learning environment, motivation and interest, and curriculum design are very high while the level of determinants of numeracy skills in terms of parental involvement, individual differences, and peer influence are high. Furthermore, the levels of mathematics competence and mathematical skills development are all very high. In addition, a relationship between the development of mathematical skills and numeracy as well as mathematics competence was found. The mathematics competence and mathematical skills development have significant relationship on numeracy skills. Therefore, both the null hypotheses are rejected. This means that these various factors influencing one’s numeracy skills play a crucial role in enhancing their overall proficiency in mathematics. Also, learners can experience significant improvements in their mathematical abilities and skill acquisition. Based on these results, it is recommended that educators and researchers explore the relationship between various determinants of numeracy skills and their impacts to enhance students' mathematical proficiency. This deeper investigation can provide valuable insights for designing effective interventions. Longitudinal studies should be conducted to understand the long-term effects of these determinants, tracking students over time to identify developmental processes and the persistence of these effects. Additionally, comparative analyses across different demographic and socio-economic groups are necessary to ensure the findings are broadly applicable. The role of evolving technologies, such as educational applications and virtual learning environments, should also be examined to determine their influence on the impact of numeracy skill determinants.