(1) Background: Endotracheal intubation in the prehospital setting is an important skill for emergency physicians, paramedics, and other members of the EMS providing airway management. Its success determines complications and patient mortality. The aim of this study was to find predictors for first-pass intubation success in the prehospital emergency setting. (2) The study was based on a retrospective analysis of a population-based registry of prehospital advanced airway management in Germany. Cases of endotracheal intubation by the emergency medical services in the cities of Tübingen and Jena between 2016 and 2019 were included. The outcome of interest was first-pass intubation success. Univariate and multivariable regression analysis were used to analyse the influence of predefined predictors, including the characteristics of patients, the intubating staff, and the clinical situation. (3) Results: A total of 308 patients were analysed. After adjustment for multiple confounders, the direct vocal cord view, a less favourable Cormack–Lehane classification, the general practitioner as medical specialty, and location and type of EMS were independent predictors for first-pass intubation success. (4) Conclusions: In physician-led emergency medical services, the laryngoscopic view, medical specialty, type of EMS, and career level are associated with FPS. The latter points towards the importance of experience and regular training in endotracheal intubation.