Despite the success of the standard functional analysis (FA), some limitations to conducting an FA in practice include time, resources, ecological relevance, and safety, which have led to the development of procedural adaptations such as trial-based and synthesized FA formats. The purpose of this case study was to identify the function(s) of self-injurious behavior (SIB) for a 3-year-old female with developmental disabilities using a brief trial-based FA with ecologically relevant synthesized contingencies, based on caregiver input, to minimize opportunities for SIB. We identified that positive physical attention likely functioned, at least in part, as a reinforcer for SIB, in less than 42 min. Overall harm to the child as a result of the synthesized trial-based FA was minimal, and the caregiver viewed the modified conditions favorably. We then assessed the role of competing stimuli on SIB rates with the child’s mother and identified two potential items that may compete with attention as a reinforcer for SIB. Our findings highlight the utility and importance of individualized assessment as the first step in the safe treatment of severely challenging behavior.