The role of the mother tongue as a medium of instruction is an important issue in second language teaching and learning and needs to be researched. The objective of this study is to investigate the use of the mother tongue in teaching and learning of second language, in this case the teaching and learning of English language at the Higher Secondary level at the Federal Government Educational Institutions in the capital territory of Islamabad. It attempts to explore the situation at government educational institutions in regard to the use of mother tongue. I used mixed method approach in this research. Questionnaire for teachers, questionnaire for students and classroom observation sheet were used for the collection of data in this study. The sample of the study comprised 400 Intermediate level students and 100 teachers teaching English at the Federal Government Educational Institutions. Chi-square tests and z-test for proportions were used to analyze the data. The data were analyzed through SPSS, Excel, and MSAT software. Results from the students’ responses show that English language teachers interact with students in Urdu very frequently in English language classes. It is also found that English language teachers use Urdu as a medium of instruction. Further, teachers’ methodology is largely limited to Grammar Translation Method. Based on the findings, it is recommended that the English language teachers need to interact with students in English more frequently. It is also recommended that English language may be used as a medium of instruction at the HSSC level. Further, it is recommended that English language teachers may be given both pre- and in-service trainings about new trends in ELT methodology.