This study examined how secondary teachers used mobile devices for teaching and learning activities in under-resourced secondary schools in Nepal. Twelve secondary teachers from three schools in the suburbs of one Himalayan district in Nepal were interviewed using qualitative research methods. The information gathered through observation of their classes supplemented the information gathered through interviews. Findings show that using mobile devices is productive for developing digital content, getting access to internet resources, and delivering lessons in the classroom. The degree of teachers' technological, pedagogical, and content knowledge was reflected in how they used their mobile devices for information access, language games, dictionaries, and specific learning applications. In the absence of desktop computers and laptops, this study demonstrated how mobile devices improved teachers' teaching and learning activities. Teachers could exhibit a greater level of proficiency in using technology if they received training on its usage in teaching and learning, and administrative support.