Legislation regarding education in South Africa has changed significantly since 1994. One aspect that has changed is language policy and language of learning and teaching at schools. The number of schools that have changed their language policy from single medium to parallel- and dual medium has increased significantly. This change had an impact on the management of schools. The head of department as an instructional leader in his or her department plays an important role in managing this change. The research aims to investigate and describe the instructional leadership role of heads of departments at parallel medium primary schools. Furthermore, this study would also focus on the impact of the leadership role of department heads when the language policy at their respective schools has changed. With the focus on instructional leadership of the heads of departments this case study investigated the challenges experienced by this department heads. The study was conducted at three parallel medium primary schools in Pretoria. This is a qualitative study which interprets data collected by three techniques. The three data collection instruments were observations, interviews and document analysis. The data were analyzed using content analysis. My findings indicate the following: First, a school's language policy has a significant influence on the instructional leadership of heads of departments at parallel medium schools. Second, more specifically, the heads of departments must do tasks and duties in both languages of learning and teaching. This implies a tremendous increase in their workload that includes planning, meetings and communication. Finally, legislation and case law forms the framework within which the heads of departments as instructional leader has to fulfill their tasks. It seems that the participants' have a limited knowledge of the legal framework.