The study examined the role of teacher capacity building and teaching effectiveness in Universal Basic Education Commission (UBEC) schools in Borno state. The study has five research objectives, five research questions and two hypotheses. The study adopted a quasi-experimental design, the population of the study comprised of five hundred (500) teachers and two hundred and fifty (150) school administrators, fifty (50) education stake holders mapped from schools and education boards across the state. A purposive sampling of two hundred (200) teachers, thirty (30) school administrators and twenty (20) education stake holders were used as a sample of the study. This is a Fair representative of a population sampling in accordance to Krejcie and Morgan (1970). The instruments used for data collection were structured questionnaires and oral interviews and phone calls. A descriptive and inferential statistics were used for data analysis. The quality of education at the basic level is largely dependent on the competence, preparedness and instructional improvement of the teachers through capacity building trainings. However, the persistent challenges of poor curriculum implementation, inadequate teaching methods, weak subject mastery, insufficient professional development opportunities and low integration of innovative teaching strategies have continued to affect teaching effectiveness and learning in UBEC schools. This study anchored on conceptual and analytical approach using existing literature, policy documents and empirical studies to explore the relationship between teacher capacity building and teaching effectiveness in UBEC schools. The study found that continuous professional development, in-service training, workshops, mentoring, supervision, ICT integration and school-based support systems significantly improve teachers’ ability to interpret and deliver effective teaching and learning across the basic education level. The paper concluded that capacity building remains a critical strategy for improving teaching effectiveness resulting in improved learner outcomes and the achievement of Universal Basic Education objectives in Nigeria. The study recommends that, there should be increased government funding for teachers professional development, institutionalized training programmes, curriculum-focused workshops, improved monitoring and supervision and the strengthening of collaboration among UBEC, SUBEB and local government education authorities (L.G.E.As).