MSc. DissertationTeaching and learning of Agricultural science subject in secondary schools have flourished over the past decades in many developing countries. The rationale for teaching the subject and the basis for its popularity is to permit students a wider set of future career options particularly farming and farming related careers than is offered by the usual academic or general subjects. Thus, this study was conducted to investigate the effectiveness of teaching and learning Agricultural science subject in selected ordinary level secondary schools in Tanzania. The specific objectives were to: assess the availability and adequacy of resources of teaching and learning; determine the adequacy of process used in teaching and learning; determine students’ knowledge, skills and attitudes acquired and determine the potential for improving teaching and learning. Data were collected from 100 student respondents, 20 Agricultural science teachers, 16 key informants and various documentary sources using questionnaires, researcher’s diary and checklists. Quantitative data were analysed using Statistical Package for Social Science (SPSS) computer programme and qualitative data were analysed by using content analysis technique. The study found that the process of implementing teaching and learning Agricultural science subject was far from what was intended by the curriculum. It was concluded that shortage of essential human and non-human resources lower teachers’ productivity and students’ achievement. It was therefore recommended that there is a need to foster the potential for continuing teaching and learning Agricultural science subject more effectively by revitalising Education for Self-Reliance (ESR) Policy which is still relevant in the country. The study also suggested undertaking further studies on effectiveness of teaching and learning Agricultural science subject in ordinary level secondary schools in other regions in order to enable generalisation of the observations.