["Psychophysiology, Volume 63, Issue 8, August 2026. ", "\nABSTRACT\nEvent‐related potentials (ERPs) have been extensively used to link neural processes with personality traits, but most work has focused on mean amplitudes, leaving intraindividual variability in brain response comparatively unexplored. The present study examined whether trial‐to‐trial variability in the P300 reflects a common latent factor across cognitive tasks, and whether it relates to personality traits in ways that differ from mean amplitude. A mixed student and community sample (N = 206) completed three ERP tasks (oddball, flanker, and doors) yielding nine P300 variants. Confirmatory factor analyses revealed that mean amplitude and intraindividual variability each loaded onto cohesive but distinct higher‐order factors, which were moderately correlated. Structural equation modeling showed that mean P300 amplitude was uniquely and negatively related to Disinhibition, consistent with prior research, whereas P300 variability showed a unique negative association with Conscientiousness, a novel finding. Furthermore, both mean P300 amplitude and P300 variability related uniquely to behavioral performance in the flanker task. This pattern of results aligns with the idea that P300 variability could indicate the consistency of attentional engagement, whereas amplitude reflects a capacity to engage top‐down control.\n"]