Objective: It has been suggested that the sequelae of trauma are under-recognized in youth on the autism spectrum. We aimed to generate expert consensus regarding important trauma indicators, including but not limited to traumatic stress symptoms, in autistic youth. Methods: We recruited 72 experts in autism and/or childhood trauma. Via a 2-round Delphi survey, experts commented on and rated the importance of 48 potential indicators, drawn from PTSD criteria and a broader literature on traumatic sequelae in autism. A revised list of 51 indicators, 18 clinical guidelines developed from expert comments, and summaries of expert qualifications and ratings from Round 1 were submitted to a second round (n = 66; 92% retention) of expert review and rating. Results: Twenty-two indicators reached consensus (>75% round 2 endorsement). Many, but not all, reflected PTSD criteria, including intrusions (e.g., trauma re-enactments in perseverative play/speech), avoidance of trauma-reminders, and negative alterations in mood/cognition (e.g., diminished interest in activities) and in arousal/reactivity (e.g., exaggerated startle). Experts also identified increased reliance on others, adaptive and language regressions, self-injurious behavior, and non-suicidal self-injury as important indicators. Consensus guidelines emphasized the need for tailored measures, developmentally informed criteria, and multiple informants to increase diagnostic accuracy. Conclusions: Expert consensus emphasizes and informs a need for tailored diagnostic guidelines and measures to more sensitively assess traumatic reactions in autistic youth.