This research examines the occupational mobility of immigrants between their countries of origin and Spain, and its main determinants. It is based on microdata from the Encuesta Nacional de Inmigrantes and the use of an international index of occupational status, the International Socio-Economic Index. The empirical evidence shows that immigrants experience, in general, an intense occupational downgrading in Spain with regard to their countries of origin. This is explained largely by the intense degradation that they often experience when they arrive, since the subsequent occupational recovery during the stay in Spain is limited. Occupational downgrading associated to the entry in the Spanish labour market is usually more severe for women, for better-educated immigrants and those from developing countries. The subsequent recovery confirms the hypothesis of a deep U-shaped occupational mobility for the last two groups, while women have greater difficulties to advance occupationally. Reside in Spain, validating foreign studies, learn Castilian and regularize the documental situation improve occupational status, but, except in the latter case, slowly. Get the first job in Spain through informal networks has a negative effect on occupational attainment. Finally, the more time looking for employment and job search including geographic mobility translates into a better occupational improvement, while unemployment has a negative effect.