Background. Pulmonary superinfections increase the mortality risk among COVID-19 patients, highlighting the need for enhanced understanding to enable early and accurate diagnosis. Methods. We present the case of a patient, a 76-year-old man, hospitalized for a severe form of COVID-19, with a ground-glass pneumonia, involving 40–45% of lung surfaces. Results. In evolution, the clinical condition worsened, presenting leukocytosis with neutrophilia, imaging towards resorption, and computer tomography images showing the appearance of pulmonary condensations in the right lower lobe, the posterior portion of the left lower lobe and pleural collections. Carbapenemase-producing Klebsiella pneumoniae was isolated from the tracheal aspirate, and the real-time polymerase chain reaction test was positive for Klebsiella pneumoniae and Legionella pneumophila. The investigations that were carried out allowed us to establish the coinfections as a probable case of Legionnaire’s disease and a ventilator-associated pneumonia with Klebsiella pneumoniae. Conclusions. The case analysis revealed that rare pneumonias may remain undiagnosed, and coinfections may be conditioned by pathophysiological factors or components of COVID-19 critical form treatment. Enhanced understanding of these aspects in clinical practice may contribute to reducing mortality risk in COVID-19 patients.