This paper presents the results of a study that links information from the prison system with information from the Spanish Social Security System in order to study the employability of former inmates of prisons in Catalonia, Spain. Few studies of this type have been carried out in the world and this is the first in Spain. The results show that 43.6 percent of ex-prisoners find a job after serving their sentence, but their integration in the labour market tends to be fragile, confirming that it is a very vulnerable group. It was also found that prison work has a favourable effect on employability and that vocational training has a lesser or no effect.