Mwambua,Benedict M.2026-02-172026-02-172025http://41.89.96.81:4000/handle/123456789/3523Science subjects are essential tools for any count1y’s industrial and technological growth. Biology is an essential discipline in the secondary school science curriculum in Kenya. However, students’ performance in Biology in Kenyan secondary schools is inferior. This poor performance may be partly attributed to the continued use of teacher-centred instructional approaches by Biology teachers, as well as to students’ low motivation. This study assessed how the Concept Mapping Teaching Approach (CMTA) influenced form four students’ achievement and motivation in Biology in selected Kitui County secondary schools. A quasi-experimental research design, employing the Solomon Four-Group model with non-equivalent groups, was used. The target population consisted of all secondary school Biology students in Kitui County. The accessible population consisted of all form four Biology students in co-educational sub- county secondary schools. Purposive sampling was used to select four co-educational secondary schools in Kitui County. The total sample consisted of 173 students, comprising 82 boys and 91 girls. Two schools were randomly designated as experimental groups and taught using the (CMTA), while the other two acted as control groups and received instruction through Conventional Teaching Methods (CTM). The study was guided by four research objectives and four null hypotheses. Data collection tools included the Students’ Motivation Questionnaire (SMQ) and the Biology Achievement Test (BAT), which were validated by two experienced secondary school Biology teachers and five science education experts. The instruments were piloted, and their reliability was estimated using Cronbach’s alpha, yielding coefficients of 0.81 for the SMQ and 0.78 for the BAT. Data analysis involved calculating means, standard deviations, one-way ANOVA, ANCOVA, and t-tests. All hypotheses were tested at an alpha level of 0.05.The study results showed that, students exposed to CMTA exhibited significant improvements in Biology achievement and motivation compared to those taught with conventional methods. It is recommended that CMTA be integrated into Biology and other science subjects to enhance students’ achievement and motivation. These findings may benefit national curriculum developers and Biology teachers by identifying effective teaching approaches that improve instructional quality and, consequently, enhance students’ achievement.»enMapping teaching approachSecondary schoolThesis