Access to affordable housing is a central urban planning goal, and housing supply and prices are strongly interlinked to land use regulation. Across the world, the past four decades witnessed a fundamental reorientation away from direct public provision of affordable housing, towards a more diversified system in which planning assumes a greater role in ensuring that the urban development process produces sufficient quantities of housing affordable to low- and moderate-income residents. The paper explores the role of planning mechanisms in achieving affordable housing outcomes and outlines the basic factors influencing effectual affordable housing delivery through the planning system. It focuses on inclusionary zoning, a land use planning mechanism that is intended to create affordable housing and foster social inclusion by capturing market resources. It presents a synopsis of the approach, and a critical analysis of the controversy it affects, by putting forward advocates’ main arguments supported by evidence from previous worldwide experiences, as opposed to critics’ arguments against it. The paper hence outlines both its benefits and major challenges for success that should be judiciously considered in designing and implementing inclusionary zoning programs.