This study explores the co-relationship of decision-making and prior professional experiences of a headteacher in dealing with challenges in the initial years of headship in a Government Secondary School in Karachi. The purpose of the study was to get insights into the process of how headteacher's decisions were informed by her prior professional experiences in coping with the challenges in the initial years of headship; and to understand the factors, other than professional experiences which tend to influence a headteacher's decisions in dealing with challenges. It is a case-study of a newly promoted female headteacher with twenty-nine years of teaching experience, posted in the same Government Secondary School. Multiple repertoire of data collection tools (interviews, observations, document analysis and reflective memos) were being used to collect informations about the inquiry. The findings of the study explored the assumption of the study that headteacher's prior professional experiences do influence her decision-making in dealing with the challenges in the initial years of headship. Moreover, it was found that decision-making processes and her prior professional experiences were co-related in teaching and learning, leading and managing the staff, efficient and effective deployment of the staff, strategic direction and development of the school, and resources and accountability. The intensity of the influence, however, varied was found very intense in three major areas of school leadership and management; in teaching and learning, leading and managing the staff and, in effective and efficient deployment of the staff. The findings depicted that a headteacher's decisions were highly dependent on her prior experiences. In the rest of the two areas, strategic direction and development of the school and, resources and accountability data showed that headteacher was dependent on others' professional expertise also. Other factors, which tend to influence the headteacher's decisions in dealing with challenges in the initial years, were found to be: pressure from high management and community, accountability, personal values and priorities, and relationships with stakeholders. The study has proposed recommendations and questions for further exploration.