Background and Objective We aimed to investigate whether viral anxiety affects insomnia severity in patients with insomnia disorder during the coronavirus disease 2019 (COVID-19) pandemic. In addition, we examined whether viral anxiety mediates the influence of dysfunctional beliefs about sleep on insomnia severity.Methods The medical records of 111 patients who visit the sleep clinic from September 2021 to May 2022 were reviewed. Patients’ symptoms were rated with rating scales including Insomnia Severity Index (ISI), Stress and Anxiety to Viral Epidemics-6 items (SAVE-6), Dysfunctional Beliefs and Attitudes about Sleep-16 items (DBAS-16), Patient Health Questionnaire-9 items (PHQ-9), Epworth Sleepiness Scale, and discrepancy between desired time in bed and desired total sleep time (the DBST index).Results The SAVE-6 score was not significantly correlated with ISI score among insomnia patients. Linear regression analysis showed that the ISI score was expected by PHQ-9 (β = 0.21, p = 0.038) and DBAS-16 (β = 0.42, p < 0.001). Mediation analysis showed that viral anxiety did not mediate the influence of dysfunctional beliefs about sleep on insomnia severity.Conclusions We could not observe the mediating effect of viral anxiety on the association between dysfunctional beliefs about sleep on insomnia severity. Though COVID-somnia was one of big issues in this COVID-19 pandemic, the influence of virus on the severity of insomnia among insomnia patients needs to be interpreted cautiously.