BACKGROUND Despite global vaccination efforts, COVID-19 still necessitates effective treatments for severe cases that can quickly escalate to life-threatening complications, such as acute respiratory distress syndrome (ARDS) and secondary pulmonary arterial hypertension (PAH). Here, we present the clinical journey of a 73-year-old Ecuadorian man who developed severe COVID-19 pneumonia complicated by an opportunistic Candida krusei infection and ARDS, subsequently progressing to long-term PAH, managed with bosentan, an endothelin 1 (ET-1) antagonist. CASE REPORT The patient, vaccinated with 2 doses of CoronaVac, experienced severe COVID-19 complications, including ARDS and secondary PAH, further complicated by a C. krusei infection. Despite prompt mechanical ventilation and intensive care, his condition rapidly deteriorated. Clinical evaluation confirmed COVID-19-associated ARDS, secondary PAH, and C. krusei infection through bronchoalveolar lavage. The therapeutic approach combined bosentan (125 mg twice daily) with dual antifungal therapy, leading to significant stabilization and eventual discharge. Post-discharge assessments showed persistent cardiopulmonary dysfunction, consistent with post-COVID-19 syndrome. CONCLUSIONS This case highlights critical COVID-19 complications in a vaccinated patient. While vaccination may provide substantial protection, COVID-19 pneumonia treated with corticosteroids can increase the risk of opportunistic infections like C. krusei, and ARDS can lead to pulmonary fibrosis and PAH. This case underscores the need for research on therapeutic strategies for complex COVID-19 cases and emphasizes comprehensive, personalized care for managing COVID-19 complications and sequelae.