Adverse childhood experiences (ACEs) have diverse effects on physical development and mental health. Previous research has focused on a dose-dependent relationship between the number of ACEs and outcomes. However, different ACEs can have varying impacts, and the subjective impact of stressors predicts outcomes. This study aimed to clarify the relationship between the quantity of ACE exposure, type of ACE exposure, and subjective level of stress felt, correlated with event-related potential activity across the scalp, while controlling for relevant confounding variables. Fifty-three participants aged 18–32 years completed questionnaires assessing their current mental health, self-regulation, childhood socioeconomic status, and history of traumatic events. Electroencephalographic activity was recorded while participants completed the Combined Attention Systems Task, a modified flanker task. Significant relationships existed between the total number of ACEs, ACE type, the subjective impact of trauma, and amplitudes during the error-related negativity (ERN) at various scalp locations. Specifically, total number of ACEs, abuse, and ‘other’ types of ACEs were associated with larger error-correct differences during the ERN timing. The subjective impact of total number of ACEs was not associated with error-correct differences, however, the subjective impact of household dysfunction, abuse, and ‘other’ ACE types were linked to error-correct differences at various scalp locations and timings. These results suggest that both the type of ACE and subjective rating are relevant to future outcomes. The effects extended beyond the ERN—affecting error-related positivity and later event-related potentials—indicating associations with the number, type, and subjective impact of ACEs across a larger time window and scalp topography.