We coproduced SPECTROM (Short-term Psycho-Education for Carers To Help Reduce the OverMedication of people with intellectual disabilities) (https://spectrom.wixsite.com/project) training for support staff (direct care workers) to help reduce the overmedication of people with intellectual disabilities, particularly the off-license use of psychotropics for behaviors that challenge in the absence of psychiatric disorders, which is a major public health concern. We hope that providing the support staff with the knowledge/skills about psychotropic medicines and non-pharmacological alternatives to address behaviors that challenge in people with intellectual disabilities through SPECTROM training will reduce staff demands for psychotropic medicines to address behaviors that challenge and improve their confidence to ask the prescribers to reduce or stop unnecessary off-license prescribing when appropriate. This should indirectly lead to the reduction of overmedication of people with intellectual disabilities. In this paper, we presented a protocol for a study that will explore (a) the scope of SPECTROM implementation by evaluating the barriers and facilitators of SPECTROM implementation and (b) the feasibility of a future large-scale cluster RCT to assess the cost and clinical effectiveness of SPECTROM training by evaluating the impact of the training and the feasibility of key processes such as recruitment, randomization, train-the-trainer, and the collection of anonymized data.