Emerging mobile technologies have significant educational benefits and raise several ethical concerns. This study examined the use and abuse of mobile phones by teachers in secondary schools in Tanzania. It employed a qualitative phenomenological research design that involved three secondary schools and 44 participants, including teachers, school heads, Teachers' Service Commission officers, Education officers, and students in Kinondoni District in the Dar es Salaam region. Data were sought through semi-structured interviews, Focus Group Discussions, and documentary reviews and were subjected to thematic data analysis procedures. The findings indicated that teachers do not fully utilise their mobile phones for academic purposes in schools. Also, abuse of mobile phones by teachers is commonplace in schools. The study recommends the need for a framework to guide teachers on the ethical use of the devices and for the curricula at all educational levels to incorporate content related to ICT use ethics.