The legal mandate to mainstream gender equality in Spain's universities has led to the establishment of gender equality units and the adoption of gender equality policy plans and protocols against sexual harassment. This research looks at how gender equality policies have been implemented within universities and what resisting and facilitating factors have hindered and promoted their implementation. These questions are addressed by studying the implementation of the 'Protocol against sexual and sexist harassment' at the biggest public Spanish university, Madrid Complutense University. Through a combination of content analysis, interviews, and a survey involving the university community, we show how the implementation of university policies against sexual harassment is dependent on a combination of factors against (obstacles/resistances) and in favour (opportunities/alliances). These factors include the form of institutionalization that gender equality took within the university, the existing formal and informal institutions, inertial resistances, and prevailing ideas about gender equality. We argue that implementation of the protocol was impeded by the scant awareness of the prevalence of harassment in daily university life, and the concomitant acceptance, by the academic community, of the phenomenon as a 'normal' practice.