Election observation has grown exponentially over the past three decades and has become a tool for legitimizing elections on a global scale. These missions have played different roles that have overlapped over time: observers are seen as doctors, police officers, judges and election experts. A great diversity of national and international actors is involved in the organization of the missions, in what has become a real professional environment. However, little is known about the concrete operation of these missions and the factors that determine how the observer’s eye is shaped. A pioneer in election observation, Latin America offers a prime field to study them. Participatory and comparative observation of the practices adopted by three types of actors (international organizations, regional organizations of electoral authorities and NGOs) in three different countries (Ecuador, Colombia and Mexico) makes it possible to show to what extent objectives, methodologies and results of these organizations differ. Contrary to the rhetoric displayed by governments, rather than a unique election observation mission, there are many points of view that depend on the role adopted by the organization and the many constraints on its work.