Bystanders play a key role in detecting, preventing, and addressing sexual harassment (SH) and other forms of gender-based violence (GBV) in university settings. This study aims to explore attitudes toward the factors that either facilitate or hinder individuals from actively intervening in situations of SH and GBV. A qualitative approach with semi-structured interviews was conducted between November 2023 and April 2024 with 89 key informants from universities in Austria, Belgium, Italy, Poland, Portugal, and Spain. Thematic analysis identified four main categories: knowledge and awareness, bystanders’ evaluation of costs and benefits, perceptions of institutional responses, and interpersonal/community factors. Findings revealed that a lack of knowledge about SH, particularly non-physical forms, was a major barrier. Increased awareness, ability to recognize signs of discomfort, self-confidence, and knowledge of support resources were key facilitators. Lack of empathy and solidarity, and fears of social judgment or professional consequences, hindered intervention, especially in situations involving power imbalances. Conversely, protective measures, such as guarantees of confidentiality were crucial in encouraging intervention. These findings highlight the need to raise awareness, create safe environments, and promote prosocial attitudes to foster a culture of active bystander intervention.