© 2018, Fundacao Oswaldo Cruz. All rights reserved. This article analyzes the debate on neo-Malthusianism and eugenics in Spanish anarchist publications in the first third of the last century. Using theoretical frameworks that have been under-utilized thus far, it provides new interpretations of what the term “eugenics” meant in pro-anarchist neo-Malthusian journals. Framed within a “struggle over meaning,” Spanish neo-Malthusianism re-signified eugenic ideas in an attempt to recover political ground that had been lost in the drive to promote individual control of human sexuality. This study also analyzes the role of the anarcho-syndicalist movement’s “direct action” strategy, in which actions undertaken by individualist anarchists were seen as a complement to revolutionary action.