Objective: Patients with panic disorder (PD) are approximately four times more likely than the general population to exhibit suicidal ideation (SI) and suicide attempts. Although prolonged duration of untreated illness (DUI) is a known risk factor for adverse outcomes in mood disorders, its impact on suicidality among patients with PD has not been well established. This study investigated whether prolonged DUI is associated with heightened SI among patients with PD, considering sociodemographic and clinical factors. Methods: A total of 804 patients with PD were recruited. DUI was defined as the time between symptom onset and the initiation of psychiatric treatment. Clinical assessments included the Scale for Suicide Ideation (SSI), Beck Depression Inventory-II (BDI-II), and Panic Disorder Severity Scale. Sociodemographic and clinical predictors of SI were examined using independent t-tests, Pearson’s correlations, and multiple regression analysis. Results: In patients with PD, the mean DUI was 41.56 months. Longer DUI was positively correlated with higher SSI total scores, along with greater depression severity. Gender women, unmarried status, and elevated BDI-II scores were significantly predicted higher SSI total scores. In the multiple regression model, prolonged DUI remained an independent predictor of SSI (B=0.116, p=0.012) after adjusting for other variables. Conclusion These findings indicate that delayed treatment contributes to increased suicidality in PD, beyond demographic and depressive risk factors. Therefore, early detection and timely intervention using treatment strategies that enhance awareness, improve the accessibility of psychiatric services, and provide social support may reduce DUI and mitigate suicide risk among patients with PD.