Background: In many large hospitals in Switzerland, adolescents 16 years and older are treated in adult emergency departments (ED). There have been few publications about this specific patient population, especially in Switzerland. This study aims to provide an overview of emergency presentations of adolescents between 16–18 years of age when compared to adults and focuses on their principle complaints. Methods: We conducted a single-centre, retrospective, cross-sectional study of all patients aged 16 years and older presenting to the adult ED at the University Hospital (Inselspital) in Bern, Switzerland, from 2013 to 2017. This analysis gives an overview of emergency presentations of adolescents between 16–18 years of age in this time period and compares their consultation characteristics to those of adult patients. Results: Data of a total of 203,817 patients who presented to our adult ED between 2013 and 2017 were analysed. Adolescents account for 2.5% of all emergency presentations. The number of ED presentations in the reviewed time period rose for adults (+2368, 95% CI: 1695, 3041, p = 0.002 consultations more per year; +25% comparing 2013 with 2017), while adolescent presentations did not significantly increase (p = 0.420). In comparison to adult patients, adolescents presented significantly more often during the night (39.1% vs. 31.5%, p < 0.001), as walk-ins (54.2% vs. 44.9%, p < 0.001), or with less highly acute complaints at triage (21% vs. 31%, p < 0.001). They were more likely to be discharged (70.8% vs. 52.2%, p < 0.001). We found a significant association between the two age groups and principle complaints. In comparison to adults, trauma and psychiatric problems were significantly more common among adolescents. Conclusions: Our data showed that complaints in adolescent patients under 18 years of age significantly differ from those in older patients. The artificial age cut-off therefore puts this vulnerable population at risk of receiving inadequate diagnostic testing and treatment adapted only for adults. Additional studies are needed on the reasons adolescents and young adults seek ED care, as this could lead to improvements in the care processes for this vulnerable population.