The purpose of this study was to examine the influence of income generating activities on teaching and learning environment in public secondary schools in Moshi Municipality, Kilimanjaro Region, Tanzania. The study was guided by innovation theory and it used convergent parallel research design under mixed research approach. Data were collected through interview, observation, questionnaire and documentary review. Quantitative data were analysed through the descriptive statistics with the help of the SPSS (Statistical Package for Social Sciences) and presented through tables, graphs and charts. Qualitative data were analysed through thematic analysis and presented through quotations and narratives. The study revealed that there are different income generating activities in public secondary schools in Moshi Municipality which include school shops, poultry farming, crop farming, stationeries, horticulture and school canteens. Also, the income generating activities that were managed well contributed to the development of teaching and learning environment in public secondary schools. The study revealed that the schools faced different challenges which hinder the effective operation of some income generating activities, thus leading to poor contribution to the teaching and learning environment. Furthermore, the study found out that motivation to students and teachers, the investment of enough capital, the allocation of enough time for income generating activities and the provision of training in all aspects of income generating activities were important strategic measures for the improvement of teaching and learning environment. The study concludes that despite the presence of income generating projects in schools, if not well managed, they will not contribute to the teaching and learning environment. The study recommends that teachers and students should be provided with knowledge and skills on how to manage income generating activities in schools to render their effectiveness.