The late positive potential (LPP), an event-related potential reflecting affective processing, may exhibit developmental shifts in magnitude and scalp location. In the present longitudinal study, 501 youth (47.3% female; 89.4% White; 12.0% Hispanic) completed the emotion interrupt task to elicit the LPP to neutral, positive, and negative images at approximately 9, 12, 15, and 18 years old (data collected 2010-2022). Multilevel growth models indicated an initial decrease in the occipital LPP and an increase in the parietal and central LPP during late childhood, with rates of change leveling off across adolescence. Trial condition (i.e., valence) significantly impacted trajectories only when the LPP was measured over occipital sites. Results provide novel evidence of stability and change in the LPP across development.