Negative affect is considered an important factor in the etiology of depression and anxiety, and is highly related to pain. However, negative affect is not a unitary construct. To identify specific targets for treatment development, we aimed to derive latent variables of negative affect and test their unique contributions to affective processing during anticipation of unpredictable, painful shock. Eighty-three subjects (43 with depression and anxiety spectrum disorders and 40 healthy controls) completed self-report measures of negative valence and underwent neuroimaging while exploring computer-simulated contexts with and without the threat of a painful, but tolerable, shock. Principal component analysis (PCA) extracted distinct components of general negative affect (GNA) and pain-related negative affect (PNA). While elevated GNA and PNA were both indicative of depression and anxiety disorders, greater PNA was more strongly related to task-specific anxious reactivity during shock anticipation. GNA was associated with increased precuneus and middle frontal gyrus activity, whereas PNA was related to increased bilateral anterior insula activity. Anterior insula activity mediated the relationship between PNA and task-specific anxious reactivity. In conclusion, GNA and PNA have distinct neural signatures and uniquely contribute to anxious anticipation. PNA, via insula activity, may relate to arousal in ways that could contribute to affective dysregulation, and thus may be an important treatment target.