Background Unplanned extubation (UE) of patients requiring mechanical ventilation in an intensive care unit (ICU) is associated with poor outcomes for patients and organizations. This study was conducted to assess the clinical features of patients who experienced UE and to determine the risk factors affecting reintubation after UE in an ICU. Methods Among all adult patients admitted to the ICU in our institution who required mechanical ventilation between January 2011 and December 2013, those in whom UE was noted were included in the study. Data were categorized according to noninvasive or invasive management after UE. Results The rate of UE was 0.78% (the number of UEs per 100 days of mechanical ventilation). The incidence of self-extubation was 97.2%, while extubation was accidental in the remaining patients. Two cases of cardiac arrest combined with respiratory arrest after UE were noted. Of the 214 incidents, 54.7% required invasive management after UE. Long duration of mechanical ventilation (odds ratio [OR] 1.52; 95% confidence interval [CI] 1.32-1.75; p = 0.000) and high ICU mortality (OR 4.39; 95% CI 1.33-14.50; p = 0.015) showed the most significant association with invasive management after UE. In multivariate analysis, younger age (OR 0.96; 95% CI 0.93-0.99; p = 0.005), medical patients (OR 4.36; 95% CI 1.95-9.75; p = 0.000), use of sedative medication (OR 4.95; 95% CI 1.97-12.41; p = 0.001), large amount of secretion (OR 2.66; 95% CI 1.01-7.02; p = 0.049), and low PaO2/FiO2 ratio (OR 0.99; 95% CI 0.98-0.99; p = 0.000) were independent risk factors of invasive management after UE. Conclusions To prevent unfavorable clinical outcomes, close attention and proper ventilatory support are required for patients with risk factors who require invasive management after UE.