Background: We aimed to identify key factors in implementing and adhering to positive behaviour support (PBS), provided by frontline staff, targeting challenging behaviours of people with intellectual disabilities living in residential group homes. Method: Using semi-structured interviews with 12 frontline staff members, we collected perspectives on a PBS training that they received. In two separate focus groups with nine frontline staff members and nine PBS trainers, we discussed factors perceived to influence PBS implementation and adherence. Hybrid coding and thematic analysis were employed. Results: Frontline staff were positive about the content of the training and noticed improvements in challenging behaviours of the people they cared for. Key factors for implementation and adherence included organisation-wide embedding of PBS, management support, motivating staff, clear documentation, regular evaluations, and additional training sessions. Conclusions: This study provides valuable insights for the implementation of and adherence to frontline staff-provided PBS.