The Department of Sociology at Peradeniya is the largest and the best-known Sociology Department in the University system in Sri Lanka. It was established in 1947. Since its establishment, the Department of Sociology grew in its reputation, academic achievement and research output. Initially the student number was deliberately kept low, but since the 1970s the enrollments increased, following the introduction of Sociology in Sinhala and Tamil media. At present, the Department of Sociology is one of the largest departments in the Faculty of Arts with well over 1000 students following Special and General degree courses. The department teaches in English, Sinhala and Tamil media and caters to a diverse student population drawn from all parts of the country. This is the only Sociology Department within the whole university system in Sri Lanka that teaches in all three media and, therefore, fully representative of the ethnic and socio-cultural diversity in the country.
Among the pioneering sociologists associated with the Department were Bryce Ryan, Gananath Obeyesekere, S.J. Tambiah, Ralph Pieris, Laksiri Jayasuriya, Nur Yalman, E.R. Leach, H.L.Seneviratne and Kitsiri Malalgoda.
The teaching and research programmes of the Department of Sociology have had a strong academic orientation in the past. Recent changes in the curriculum and research activities of the staff indicate a deep concern with high priority national issues such as poverty, development, health, conflicts resolution and resettlement of people displaced by development schemes, war and natural disasters like tsunami.
In 2004 the Department came first in a nationwide competition for awards for improving the quality and relevance of undergraduate education under the World Bank-funded IRQUE scheme. Under this scheme, the department has embarked on a major project for curriculum and infrastructural development, partnerships with development agencies, internship for students, and post-graduate training of staff.