Background There is a lack of research on trauma in people with intellectual disabilities. This study assessed expert consensus on the traumatic potential of a broader range of adverse life events, and differences in symptom manifestation and behavioural symptom equivalents of post‐traumatic stress disorder (PTSD) symptoms. Method The present authors conducted a three‐step Delphi survey using a mixed‐methods design. Twenty‐nine expert raters participated in the survey, and 16 persisted to the final round. Consensus was calculated using the interquartile range. Results Traumatic potential was attributed to adverse life events, particularly revolving around sexuality and autonomy. DSM‐5 symptoms of PTSD were rated as partially adequate, with behavioural symptom expression being the main difference to the general population. Conclusion The range of traumatic events should be broadened for people with intellectual disabilities. A specific subset of events need to be defined in future research. Detection of PTSD depends upon determining specific symptom correlates of challenging behaviour.