Background: Staff working with clients with intellectual disabilities (ID) who display challenging behaviour may contribute to the continuation of this behaviour, because it causes emotional reactions such as anxiety, anger and annoyance, which may prohibit adequate response behaviour. To enhance staff behaviour and treatment skills a training that aimed at improving emotional intelligence (EQ) was developed. Aim: The goal of this study was to assess whether an EQ training in combination with a video-feedback training programme improves emotional intelligence of staff working with clients with ID and challenging behaviour. Methods: Participants were 60 staff members working with individuals with ID and challenging behaviour. Thirty-four staff members participated in a 4-month training programme and 26 constituted the control group. A pretest-posttest control group design was used. Effectiveness was assessed by using the Dutch version of the Bar-On EQ-i and the judgments of experts on emotional intelligence. Results: Emotional intelligence of the experimental group changed significantly more than that of the control group. Judgments of experts on emotional intelligence indicated that the change of emotional intelligence of the experimental group improved positively. Conclusions: The positive effect of the training programme on emotional intelligence is consistent with previous research on emotional intelligence and suggests that emotional intelligence of staff working with clients with ID and challenging behaviour can be influenced by training.