Objectives: Insertion of a temporary transvenous pacemaker (TTPM) is one of the life-saving interventions performed in the emergency department (ED). The aim of the study was to determine demographic, clinical characteristics, and in-hospital outcomes of patients who underwent TTPM insertion due to hemodynamically unstable bradyarrhythmia in the ED. Methods: In our study, 234 consecutive patients who underwent TTPM insertion at the bedside in the ED between January 2014 and October 2019 were included in the study. Etiological characteristics, electrocardiographic (ECG) findings, requirements for permanent pacemaker (PPM), and in-hospital mortality of the patients were analyzed retrospectively. Results: Extrinsic causes were the most common etiology of unstable bradyarrhythmia (57.6%). Most extrinsic causes were drug therapy-related factors (60.7%). Bradyarrhythmia persisted in 60% of patients after extrinsic causes were eliminated. The most common ECG finding was a high-degree atrioventricular block (62%). PPM was implanted in 44% of patients. In-hospital mortality rate was 19.7%. In the multivariate regression analysis, the left ventricular ejection fraction (LVEF) and diastolic blood pressure (DBP) measured at admission (p<0.001 and p<0.001, respectively) were determined to be independent predictors for in-hospital mortality. Conclusion: First diagnosis and intervention in the ED are of great importance for patients with unstable bradyarrhythmia. The fastest possible TTPM insertion in the ED can reduce mortality by reducing the exposure time to hypoperfusion of vital organs, especially in patients with reduced LVEF and low DBP. Furthermore, it should be kept in mind that an underlying latent conduction system disease can also be present in bradyarrhythmias thought to occur potentially due to extrinsic factors.