Repetitive negative thought (RNT) is a transdiagnostic process that predicts the onset, severity, and recurrence of several psychiatric disorders, including anxiety and depression. Despite progress in understanding the affective consequences of RNT, the mechanisms through which RNT contributes to clinical symptoms are not well understood. Executive function (EF), a set of cognitive processes that contributes to the organization of cognition and the regulation of emotion, was hypothesized to enhance the effect of RNT on negative affect (NA), a core symptom shared by anxiety and depression. The present study used latent variable modeling and hierarchical linear regression to test the contributions of RNT, EF, and their interactions to NA. Consistent with hypotheses, high levels of RNT were associated with higher NA, and EF deficits enhanced this association. Results provide evidence that the RNT-EF interaction represents a pathway in the development of NA, and by association, anxiety and depression.