This essay explains that López-Aranguren’s intellectual relationship with Marxism is quite symptomatic of a whole generation of young but influential fascist figures that eventually evolved towards liberal and reformist positions. Although he never was a Marxist thinker, Aranguren published El marxismo como moral in 1968 as a strategic intervention in some of the cultural and political debates that galvanized the Spanish intellectual life during the last years of Franco’s regime. On one hand, it is evident that this philosopher did not want to lose any relevance among a young generation of (more or less) radicalized university students, writers and activists. Marxism was, in the late 1960s, the theoretical idiom to establish this dialogue. On the other hand, Aranguren did not sympathize with those humanist and existentialist trends of Marxism that had an important moral, behaviorist, operational, revolutionary and individual dimension. According to this thinker, who gained his philosophical prestige in the field of moral philosophy, one had to purge Marxism of its ethical, utopian, and even emotional-psychological aspects in order to embrace a more sober, austere, realist, and limited version of this school of thought. Aranguren found this version in Althusser’s recently and successfully published texts in Paris. However, Aranguren’s approach to Althusser is revealingly idiosyncratic since its function in El marxismo como moral consists in emphasizing a centrist type of political possibilism that could counteract a left-wing, radical Marxism, eager to conceive the end of the dictatorship as a revolutionary opportunity for a voluntarist and collective political subjectivity.