The integration of e-learning platforms into secondary school instruction has been widely promoted as a means of enriching teaching practice, yet the extent to which teachers actually change how they plan, deliver, and assess lessons following the introduction of such platforms remains an empirical question that varies considerably across school contexts. This study examined the effect of e-learning platforms on teachers’ teaching practices in secondary schools, using Kiziranfumbi Secondary School as a case study, guided by objectives that sought to establish the level of teachers’ adoption and use of the e-learning platform, assess changes in teaching practices associated with platform use, determine the relationship between e-learning platform use and teaching practices, and identify the challenges teachers face in integrating the platform into their instructional practice. A descriptive correlational research design combining quantitative and qualitative approaches was adopted, with data collected from a sample of 58 respondents comprising teachers, the head teacher, and the director of studies, using questionnaires, interviews, and lesson observation. Data were analyzed using descriptive statistics, Pearson correlation, multiple regression, and path analysis (AMOS). Results showed moderate-to-high adoption of the e-learning platform for lesson preparation and delivery (mean = 3.64) and a significant positive correlation between platform use and teaching practices (r = 0.601, p < 0.01). Regression analysis showed that platform use and teacher ICT competence jointly explained 45.2 percent of the variance in teaching practices (R² = 0.452). Path analysis revealed that teacher ICT competence significantly mediates the relationship between e-learning platform use and teaching practices, with a significant indirect effect (β = 0.238, p < 0.01) alongside a significant direct effect (β = 0.329, p < 0.01), yielding a total effect of 0.567. The study concludes that e-learning platform use has meaningfully, though moderately, influenced teaching practices at Kiziranfumbi Secondary School, operating both directly and through its effect on teachers’ ICT competence, and recommends targeted ICT skills training for teachers, improved access to functional devices and internet connectivity, and continuous pedagogical support for integrating e-learning tools into classroom practice.