This study investigated individual differences in responses to disasters based on participants’ motivational reactivity and ethical ideology. Motivational reactivity was measured using the motivational activation measure (MAM), which assesses individual differences in appetitive and defensive system activations. Participants (N = 240) answered survey questions about how they would respond to natural disasters or emergency situations. Results showed that (1) participants with higher defensive activation scores were more likely to report they would share warnings during a disaster situation, (2) high appetitive system activation is associated with high ethical relativism, (3) high defensive system activation is associated with high ethical idealism, and (4) individuals’ personal moral philosophy moderates the effects of MAM score on intention to warn others. Theoretical and practical implications are also discussed.