Background: Recent research addressed the relationship between staff behaviour and challenging behaviour of individuals with an intellectual disability (ID). Consequently, research on interventions aimed at staff is warranted. The present study focused on the effectiveness of a staff training aimed at emotional intelligence and interactions between staff and clients. The effects of the training on emotional intelligence, coping style and emotions of support staff were investigated. Method: Participants were 214 support staff working within residential settings for individuals with ID and challenging behaviour. The experimental group consisted of 76 staff members, 138 staff members participated in two different control groups. A pre-test, post-test, follow-up control group design was used. Effectiveness was assessed using questionnaires addressing emotional intelligence, coping and emotions. Results: Emotional intelligence of the experimental group changed significantly more than that of the two control groups. The experimental group showed an increase in task-oriented coping, whereas one control group did not. The results with regard to emotions were mixed. Follow-up data revealed that effects within the experimental group were still present four months after the training ended. Conclusions: A staff training aimed at emotional intelligence and staff-client interactions is effective in improving emotional intelligence and coping styles of support staff. However, the need for more research aiming at the relationship between staff characteristics, organisational factors and their mediating role in the effectiveness of staff training is emphasised.