Intravenous rapid injection of fentanyl causes respiratory depression (severe apneas), leading to sudden death, which constitutes the deadliest drug reaction among overdoses of synthetic opioids. Here we asked whether acute inhalation of overdose fentanyl would also result in similar respiratory failure and death. The anesthetized and spontaneously breathing rats with tracheal cannulation were exposed to aerosolized fentanyl at 100 mg/m3 (FNTH) or 30 mg/m3 (FNTL) for 10 min. Minute ventilation (VE), electromyography (EMG) of the internal and external intercostal muscles and thyroarytenoid muscles (EMGII, EMGEI, and EMGTA), heart rate and arterial blood pressure were recorded. During the exposure, FNTH and FNTL immediately triggered bradypnea (40 % reduction, p < 0.05) with TE prolonged and then gradually decreased VE by 40 % (P < 0.05) after a brief VE recovery. The initial TE prolongation (apneas) were characterized by the cessation of EMGEI activity with enhanced tonic discharges of EMGTA and EMGII. After termination of the exposure, the cardiorespiratory responses to FNTL returned to the baseline values 30 min later, while those to FNTH were greatly exacerbated (P < 0.05), leading to ventilatory and cardiac arrest occurred 16.4 ± 4.7 min and 19.3 ± 4.5 min respectively after the onset of FNTH. The ventilatory arrest was featured by cessation of both EMGEI and EMGII and augmentation of tonic EMGTA. Our results suggest that acute exposure to an overdose of fentanyl aerosol leads to death through initially inducing a brief central and upper airway obstructive apnea as well as chest wall rigidity followed by gradual severe hypoventilation, bradycardia and hypotension, and eventual cardiorespiratory arrest in anesthetized rats.