This note on Social Impact Assessment (SIA) is part of a series of guidance and good practice publications prepared by the Inter-American Development Bank’s Environmental and Social Safeguards Unit (ESG). The series covers assessment and management of environmental and social risks and opportunities, and aims to provide guidance on international good practice and IDB’s requirements in applying environmental and social sustainability principles. Undertaking an SIA is an essential part of preparing and implementing development projects. The SIA provides the information needed to enhance development outcomes, assess and manage potential risks, and strengthen social acceptance and support to a project. This note attempts to systematize and summarize the emerging international consensus on what an SIA process should consist of, and to provide guidance and greater clarity about how to integrate attention to social safeguards issues more in IDB’s project planning and implementation. By applying the approach presented in this note, it is expected that the quality, consistency, and operational relevance of SIAs will improve