This study addresses the gap in the existing literature about what teachers at secondary level in Pakistan know about formative assessment and to what extent they are using formative assessment results to make instructional adjustments in their teaching to address gaps in students’ learning. This is a qualitative study and the research in this study was done on a purposive sample of 21 teachers, using semi structured interviews in which open-ended questions were asked to answer the questions about use of formative assessment. The research results suggest that most teachers had a comprehensive understanding of formative assessment as continuous or ongoing assessment which is taken during studies, and which can be used to identify gaps in students’ learning. This research also concluded that formative assessment guides teachers on how to modify their instruction to address these gaps in learning during instruction, rather than waiting till it is too late. This study elaborates on how formative assessment is implemented in the class, and on how effectively the results of assessment are used to address gaps in students’ learning and what are the challenges in implementing and using formative assessment results.