Teacher leadership has emerged as a powerful tool to enhance student learning outcomes in the context of developed countries; however, there is a need to study teacher leadership activities in the classroom in the context of Pakistan, with special reference to Gilgit-Baltistan. Hence, this study was designed to explore teachers' leadership activities in the classroom in a private high school in Gilgit-Baltistan. This was a qualitative study within which a case study was used as a research method. The research participants were selected through purposive sampling which included head teacher, two secondary school teachers and six students of class ten. The fieldwork was spread over six weeks to collect relevant data. In this regard, semi-structure interviews, classroom observations and focused group discussions as tools for data collection were used. An activity theory was used as a lens to analyse the data within adapted teacher leadership frame work by Farman and Mackenzie (2010). Key findings include continuous professional capacity building promotes teachers' leadership, teacher leadership promotes relationships with students, teacher leaders translate curriculum into learning activities, teacher leadership activities enhance students' self-esteem and confidence to solve learning problems, teacher leaders' pedagogic act contributes to students' leadership qualities, school policies and teachers' workload affect teachers' leadership activities, and teacher leaders develop culture for leadership activities in the classroom. The study also proposes a possible framework for teachers' leadership activities in the classroom for student learning. The study suggests a viable approach for making school policy enabling teachers to act as teacher leaders. The study also suggests making continuous professional development mandatory for teachers to carry out their leadership activities in the classroom for purposeful student learning.