Educators' competences in Education for Sustainable Development (ESD) is a growing field of study. Still, critics warn that competence frameworks should not be used as a technical prescription without reflecting on the complexity of the educational setting. This study aims to shed light on the competences that educators in ESD, across both formal and non-formal educational settings, perceive as necessary for their role while analyzing how their motivations and challenges are interlinked with their ESD competences. These issues are explored through 18 online interviews with ESD educators within the Barcelona Metropolitan Area in Spain, where multiple and diverse ESD settings co-exist. Atlas.ti was used for the content analysis. Results show that a diverse set of competences was persistently perceived among participants as necessary. Across both formal and non-formal contexts, the role of competences such as "Transdisciplinary" and "Empathy" was especially interlinked with their motivations and challenges. Nonetheless, competences such as "Systems" were more relevant in the formal setting, while "Participation" was emphasized in the non-formal context. We discuss the various ways that educators perceive ESD competences as necessary, which are influenced by their working settings (e.g. formal and non-formal), but also their particular pedagogical challenges and individual motivations for proper diagnosis and training.