Much has been said and written about the nature of teachers' workplace relationship, particularly the role of their collaborative activities in schools, but it has been largely limited to the West. There is dearth of studies in the area of teacher collaboration in developing countries in general and Pakistan in particular. This study, is therefore, set out to explore the nature of teacher collaboration in a private secondary school in Karachi, Pakistan. Using case study approach, the whole school was chosen as a case. In that school, 11 teachers participated in the study. The aim of the study was to explore the existing practices, the facilitating and the impeding factors for teacher collaboration. The data were collected through individual and focus group interviews, observations, which were supplemented by informal talks and analysis of the relevant documents. The major findings of the study revealed that teacher collaboration exists in the form of formal (e.g. professional meetings, planning session, in and out of school workshops), and informal (e.g. break time discussion and spontaneous meetings), which are facilitated by administrative arrangements in the school. The study found that school head, school structure, and teachers' motivation play important roles in making teachers to work together. However, teacher turnover, shortage of human resources and product- oriented examination system were found to be major challenges in promoting a collaborative culture in the school. Moreover, the study shows that though improved classroom practices of teachers are both desirable and possible, depending on the acquisition of ;(i) pedagogical skills, (ii) their ability to reflect on their practices, and (iii) the opportunities to share their experiences and views with each other. It is suggested that, collaboration can become reality in our schools, if we have planned formal and informal discussions based on the data obtained from monitoring the classroom practices, support from school leaders and teachers' motivation towards their professional development. The study also generates opportunities for further research.