Ruminative brooding is a transdiagnostic symptom defined as repetitive dwelling on thoughts and emotions, and has been linked to emotion dysregulation, maladaptive metacognitive beliefs, and abnormal interoception, but the relative contributions of these factors and their neural mechanisms remain unclear. We used source-localized resting-state EEG analyses (n=31) to map these processes onto cross-frequency coupling (CFC) networks. We first identified symptoms of interest for CFC analyses by employing regularized symptom network analyses which revealed two clusters relevant to brooding: one dominated by interoceptive/mindfulness dimensions and another by metacognitive/emotional dysregulation, with brooding aligning with the latter. We then examined links between representative symptoms from each cluster and resting-state cross-frequency phase–amplitude coupling (PAC) using partial least squares (PLS) correlation. Emotional dysregulation and brooding were associated with delta-beta PAC, whereas mindfulness symptoms related to beta-gamma and theta-gamma PAC. For the brooding/dysregulation signature, prefrontal and cingulate phase activity modulated amplitudes in regions implicated in emotion regulation and interoception (e.g., subcallosal cingulate, somatosensory cortex, insula, parietal cortex). The mindfulness/interoception signature reflected coupling within networks supporting interoceptive awareness and emotion regulation. Overall, our results indicate that brooding is more tightly linked to maladaptive metacognitive beliefs and emotional dysregulation than to mindfulness/interoception, consistent with resistance toward one’s thoughts and emotions. Neurally, this may be reflected by compensatory top-down control from prefrontal and cingulate areas over interoceptive, affective, and self-referential systems, pointing to the potential value of therapies that cultivate self-acceptance and modify maladaptive metacognitive beliefs for reducing rumination.