Background: According to the guidelines for treatment of multiple trauma patients, immobilization of the neck and neck collar fixation are essential. However, following neck collar fixation patients usually experience dyspnea. Some studies have found that neck collar fixation can lead to decreased pulmonary volumes, yet there have been no studies on the effect of neck collar fixation on patient ventilation. Objectives: The purpose of this study was to determine the effect of neck collar fixation on ventilation in multiple trauma patients. Methods: This study was a descriptive-analytical study, which was performed in the emergency department of Tabriz University of Medical Sciences on multiple trauma patients with a Glasgow Coma Score (GCS) of 15. The effect of neck collar fixation on ventilation in the study participants was examined with the use of capnography. Results: This study involved 163 multiple trauma patients. Of these, 65% were male. The mean of end tidal carbon dioxide (ETCO2) of the patients without neck collars was 34.62 ± 4.46 and the mean ETCO2 of the patients with neck collars was 34.21 ± 2.31. There was no significant difference between the means of ETCO2, before and after removing the neck collar, among the studied patients (P = 0.196). Conclusions: According to the results of our study, neck collar fixation has no effect on ventilation in multiple trauma patients.