Self-affirmation reduces defensive responding to self-threats. The present study extended beyond self-threats to assess affirmation's influence on responses to negative emotional pictures as measured by the late positive potential (LPP), an event-related potential in the encephalogram that reflects motivational significance. Participants completed a trait measure of behavioral inhibition system (BIS) sensitivity. Then they affirmed (or did not affirm) a core personal value before viewing a series of emotionally evocative pictures. Affirming a core value increased LPP responses to negative emotional pictures among individuals higher in BIS. Self-affirmation thus appeared to alter the motivational significance of negative pictures among threat-prone individuals, consistent with a reduction in the defensive avoidance of aversive stimuli. These findings suggest that affirming values may influence responses associated with basic (non-self) motivational systems among individuals sensitive to threat.