Background Emergency tracheal intubation is routinely performed in the prehospital setting. Airway management in the prehospital setting has substantial challenges. Objective The aim of the present study was to determine risk factors predicting tracheal intubation–related complications on the prehospital field. Setting A prospective, multicentric, cohort study which was conducted in three mobile ICUs (MICUs; service mobile d’urgence et de réanimation).Outcome measures and analysis Tracheal intubation–related complications were defined as the occurrence of at least one of the following events: oxygen desaturation (SpO2 < 90%) during tracheal intubation, aspiration (regurgitation visualized during laryngoscopy), and vomiting. Difficult intubation was defined as more than two failed direct laryngoscopic attempts, or the need for any alternative tracheal intubation method. Multivariate logistic regressions were used. Results During the 5-year study period, 1915 consecutive patients were intubated in the MICUs participating in the study. Overall, 1287 (70%) patients were successfully intubated after the first laryngoscopic attempt, with rates of 90, 74, 42, and 30% for Cormack–Lehane grade 1, 2, 3, and 4, respectively. Tracheal intubation was difficult in 663 cases (36%). Tracheal intubation–related complications occurred in 267 (14%) patients. In the multivariate analysis, we found that the leading risk factors for tracheal intubation–related complications were Cormack and Lehane grade 3 and 4 [odds ratio (OR) = 1.65; 95% confidence interval (CI), 1.05–2.61; and OR = 2.79; 95% CI, 1.56–4.98, respectively], a BMI of more than 30 (OR = 1.61; 95% CI, 1.13–2.28), when intubation was difficult (OR = 1.72; 95% CI, 1.15–2.57), and when tracheal intubation required more than one operator (OR = 2.30; 95% CI, 1.50–3.49).Conclusions In this prospective study, we found that Cormack and Lehane more than grade 2, BMI >30, difficult intubation, and tracheal intubation requiring more than one operator were all independent predictors of tracheal intubation–related complications in the prehospital setting. When these risk factors are identified on scene, adapted algorithms that anticipate the use of a bougie should be generalized to reduce morbidity on the prehospital field.