This study examined the attitudes of public junior secondary school teachers in Kamukunji Sub-County, Nairobi County, towards the implementation of the Competency-Based Curriculum (CBC). Employing a convergent parallel mixed-methods design, the research was grounded in John Dewey's Constructivist Theory. A sample comprising five schools, five principals, 46 teachers, and one Quality Assurance and Standards Officer (QASO) participated. Data were gathered through questionnaires, interviews, document analysis, and observations, and were rigorously tested for reliability and validity using Cronbach's Alpha, member checking, and triangulation. The findings revealed that teachers' attitudes play a critical role in the successful implementation of the CBC, with positive attitudes being key to its effective adoption. The study recommends targeted professional development programs to improve teacher preparedness, better resource allocation to support the curriculum, enhanced collaboration with educational stakeholders, and ongoing evaluation and feedback mechanisms. These strategies are essential to ensuring the long-term success of CBC implementation in Kamukunji Sub-County. Keywords: Competency-Based Curriculum (CBC), Teacher attitudes, Curriculum implementation, Professional development, Resource allocation, Educational stakeholders, Teacher readiness, Continuous evaluation.