Black individuals had lower baseline skin conductance levels and startle than Whites. No racial differences in physiological reactions to threat. Hispanic and Black participants exhibited greater amygdala connectivity to dorsolateral PFC, dorsal anterior cingulate cortex, insula, and cerebellum than Whites. No differences in amygdala reactivity to fearful versus neutral faces across races. Amygdala connectivity associated with 3-month PTSD symptoms differently by racial/ethnic group. Racial group differences in connectivity partly driven by structural inequities. Variability in tonic neurophysiological arousal differs between racial/ethnic groups post-trauma. Lower amygdala-salience network connectivity in Whites compared to Hispanics and Blacks. Amygdala connectivity partly mediates PTSD susceptibility varying by race.