The manifestation of severe pneumonia is only occasional, and pneumomediastinum is a condition that occurs rarely in Coronavirus disease 2019 (COVID-19) patients, especially in those patients who are infected with the Omicron variant. In addition, whether severe pneumonia or pneumomediastinum often occurs in patients in older age, in poor physical condition, or with underlying diseases remains to be ascertained. To date, severe pneumonia and pneumomediastinum due to Omicron infection had not been reported in a young patient with an excellent physical condition. In this study, we report such a case with the aforementioned manifestations in a robust adolescent infected with Omicron BA.5.2.