Background: In contrast to pre-sleep cognitive arousal, self-reported pre-sleep somatic arousal is a rather elusive construct for which little validity has been provided. Thus, the clinical significance of somatic symptoms during the pre-sleep period remains unknown. Participants: 248 patients (45.0 ± 16.7 years old, 65.3% female) with a diagnosis of chronic insomnia disorder, out of 388 consecutive patients evaluated at the Behavioral Sleep Medicine (BSM) program of Penn State Hershey Sleep Research & Treatment Center. Methods: Participants completed the Pre-sleep Arousal Scale assessing cognitive (PSAS-C) and somatic (PSAS-S) arousal as well as the Insomnia Severity Index (ISI), Ford Insomnia Response to Stress Test (FIRST), Arousal Predisposition Scale (APS), and Depression Anxiety Stress Scale (DASS). Multivariable stepwise regression assessed which clinical factors were independently associated with greater PSAS-C and PSAS-S scores. Receiver operating characteristic analysis determined the predictive value for identifying sleep reactivity (FIRST≥18) and clinical anxiety (DASS-A ≥ 10) and clinically useful cutoff scores. Results: The strongest correlates of PSAS-S were DASS-A (β = 0.64) and chronic pain (β = 0.11), while those of PSAS-C were FIRST (β = 0.29) and a history of stroke (β = 0.10). A PSAS-S score of 14.8 (AUC = 0.87, 95%CI = 0.83-0.91) and a PSAS-C score of 24.5 (AUC = 0.82, 95%CI = 0.76-0.88) showed the best balance in specificity and sensitivity to identify clinical anxiety and sleep reactivity, respectively. Conclusions: Self-reported pre-sleep somatic symptoms are a marker of comorbid anxiety and, potentially chronic pain, impacting nighttime sleep. The optimal cutoff scores of 14 and 20 proposed herein can help clinicians with case formulation, with tailoring BSM treatments and their targets.