Background: The COVID-19 pandemic, in addition to being a catastrophic global health crisis, has caused disharmony in the operation of Greek public hospitals, especially at an administrative and financial level. Specifically, due to the excessive increase in demand for hospital services, challenges related to meeting the needs of hospitals in logistical equipment and staffing arose significantly, a situation which threatened the proper operation and sustainability of an already tested health system. To address this threat, measures and policies were implemented to support the Greek National Health System. Purpose: The purpose of this thesis is to describe the effects of the pandemic on the efficiency and effectiveness of Greek public hospitals. Research Methods: The research, covering the years 2019 to 2021, was carried out based on nursing care data, general financial data of revenues and expenditures as well as financial data obtained from the published financial statements of the primary reference hospitals for COVID-19, per health region. Findings: During the ongoing COVID-19 pandemic, public hospital revenues became heavily dependent on government funding to cope with the high costs that incurred. The successful response of hospitals to future crises depends on the adoption of structural changes of the national healthcare system, Furthermore, the two fundamental weaknesses of the Greek hospitals: delay in the collection of hospital claims and increased expenses should be addressed with great care. The healthcare stakeholders in Greece should ponder on the chronic phenomenon of the inability to collect hospital claims from EOPYY (the single purchaser for publicly funded health services), the adoption of a more realistic reimbursement system such as the DRG’s but also the cutdown of expenses with the use of biosimilar drugs and the use of telehealth for non-emergency chronic patients.