This paper analyzes, on the one hand, the vulnerability that migrant workers face due to the change in social security systems when moving from one State to another, specifically focusing on old-age, disability and survival pension benefits as part of the social security and, on the other hand, the proposals and existing mechanisms to reduce the margin of vulnerability of migrant workers. In this sense, international conventions, both bilateral and multilateral, on social security are analyzed as the main response and mechanism at the international level, but also are discussed their main difficulties and limitations. In the same way, other proposals and possibilities to achieve greater coverage for this type of workers are exposed.