Economic development activities change the physical and social environments in which individuals live. For planners, it is important to anticipate the types of changes that might occur, and to put measures in place that mitigate negative impacts and promote positive impacts on people and communities. Social Impact Assessment (SIA) was introduced as a tool for understanding the social impacts of development. There are three factors, however, that limit the use of SIA in developing countries. First, the original SIA tool was designed in a developed country, and as such the list of indicators developed may not suitable for local conditions. Second, there is no specific theoretical underpinning of the SIA tool, and thus no link between the SIA tool and particular theories of social behaviour. Third, there is no particular link between what SIA measures, and what should be done to mitigate the effects of development activities. The purpose of this paper is to address these three issues and in doing so, provide a SIA tool that can be applied usefully and practically in a developing country. The theoretical basis of SIA used in the paper is Actor-Network Theory (ANT). The tool, which was developed using ANT, principles consists of five stages of analysis: identification of principal actors (human and non-human) and the changes due to development; exploration of the ownership of resources (capital) that enables principle actors to change; identification of change agents attached to the capital of principal actors; tracing which interests of actors are aligned to deal with the development; and an analysis of the social change platform (mobilization of actors) based on connections of all principal actors with other actors. Each of these stages provides the basis for determining what should be assessed in SIA, how to structure the assessment, and how to interpret the results of a SIA.