Appropriate responding to threat and reward is essential to survival. The nucleus accumbens core (NAcc) is known to support and organize reward behavior. The NAcc is also necessary to fully discriminate threat and safety cues. To directly reveal NAcc threat firing, we recorded single-unit activity from 7 female rats undergoing Pavlovian fear discrimination. Rats fully discriminated danger, uncertainty, and safety cues, and most NAcc neurons showed greatest firing change to danger and uncertainty. Heterogeneity in cue and reward firing led us to identify distinct functional populations. One NAcc population signaled threat, specifically decreasing firing to danger and uncertainty cues. A separate population signaled bidirectional valence, decreasing firing to the danger cue (negative valence), but increasing firing to reward (positive valence). The results reveal the NAcc to be a source of threat information and a more general valence hub. SIGNIFICANCE STATEMENT The nucleus accumbens core (NAcc) is synony...