Exposure therapy for anxiety disorders is translated from fear conditioning and extinction. While exposure therapy is effective in treating anxiety, fear sometimes returns after exposure. One pathway for return of fear is reinstatement: unsignaled unconditional stimuli following completion of extinction. The present study investigated the extent to which valence of the conditional stimulus (CS+) after extinction predicts return of CS+ fear after reinstatement. Participants (N = 84) engaged in a differential fear conditioning paradigm and were randomized to reinstatement or non-reinstatement. We hypothesized that more negative post-extinction CS+ valence would predict higher CS+ fear after reinstatement relative to non-reinstatement and relative to extinction retest. Results supported the hypotheses and suggest that strategies designed to decrease negative valence of the CS+ may reduce the return of fear via reinstatement following exposure therapy.