Dengue is one of the most critical public health hazards which has made severe impacts in the recent past in Sri Lanka. The Government of Sri Lanka (GOSL) is very keen on implementing many programmes and policies to control and prevent Dengue. Thus, community participation is one of the key strategies which is keenly followed by the government in the successful Dengue prevention activities. Even though, Dengue has been a contested health hazard in the recent past, and number of preventive measures have been implemented by the government to control Dengue, the expansion of Dengue hazard is still obvious and the impacts also severe and wider. Many people have been victimized in terms of hospitalization and death in the island and numbers of people have been affected by Dengue in the Kalmunai Regional Health Services (RDHS) area. Therefore, this study is significant as it explores why community participation, as a Dengue preventive measure, could not be effective in the Kalmunai RDHS area, even though the RDHS has been equipped with technical and human resources. The main objective of the study is to assess the level of community participation in Dengue prevention in the Kalmunai Regional Health Services (RDHS) area, and to identify factors affecting community participation in Dengue prevention, and to understand how villagers reacted to Dengue prevention activities. The information and data for this research have been gathered from a desk analysis and a field survey (interview, questionnaire, and Focus Group discussions). Data have also been collected from structured interview with key informants. Secondary data have been gathered from Divisional Secretariat, RDHS and MOH records, books, publications, journal articles, e-sources, previously conducted research and reports, and other relevant documents. Through data analysis, this study found that the community participation in Dengue prevention activities could not be effected in Kalmunai regional health services area, and further, this study found that there are many factors affecting community participation in dengue prevention programs in the Kalmunai region. The carelessness in community health, lack of social capital, lack of community ownership and individualism, challenges of gender equity in terms of cultural barriers or restrictions and expecting money are the key factors identified as reasons for their poor participations in dengue prevention in the area of research.