The coronavirus disease 2019 (COVID-19) pandemic have an impact on healthcare systems. A Mixed method study was used to explore 1) situation analysis of COVID-19 pandemic in Bangkok and metropolitan region 2) health system management COVID-19, problems and obstacles 3) lessons learned from the management of COVID-19 pandemic and 4) policy synthesis for the tertiary health service systems in COVID-19 pandemic in Bangkok and metropolitan region. Data were collected during from week 14 to week 54 in 2021. Quantitative data were collected from Co-lab and Co-ward. Qualitative data were collected by in-depth interview and focus group discussion. 126 purposive participants were conducted from hospital administrators or hospital representative, assessors, and multidisciplinary team in health care services. Descriptive statistics were used for quantitative data and content analysis were used for qualitative data. The results show that: 1. The situation analysis of COVID-19 pandemic in Bangkok and metropolitan region, the highest infected rate in Bangkok were found in week 32 (14,373 person/week or average number 2,053 person/day). Similarly, in metropolitan region, 183,558 infected persons reported on week 32. The highest infected persons reported on Nonthaburi, Samut Prakan and Samut Sakhon (54,998, 34,499 and 30,373 respectively). The registered hospital bed in Thailand were 154,942 beds, the bed capacity in Bangkok were reported 14.28 % and total bed capacity in Bangkok and metropolitan region addressed 23.01% of registered hospital bed. 2. The health system management COVID-19, problems and obstacles in Bangkok and metropolitan region, 2.1 service delivery: The hospitals adapted healthcare services under the concept of Incident Command System (ICS) in response to public health emergencies. Moreover, they modified some places to support many infected patients, postponed non-covid and non-emergency cases, developed clinical practice guideline, and making change in working methods follow the dynamic of situation. The participants reported service delivery barriers such as no service coverage during high infected rate, limited expertise due to emerging disease, people more afraid of catching COVID-19, non-collaboration between organizations across different sectors, lack of unity, and limited quality services. 2.2 health workforce: The hospitals reduced workload for responding to COVID-19, pooled the workforce, and managing appropriate role. In addition, developed competencies of healthcare providers, ensuring health care professionals safety, and providing reward. The informants reported health workforce barriers for example work overload and lack of health workforce during high infected rate, and fear during the first outbreak of COVID-19 pandemic 2.3 Information: The COVID-19 pandemic required health information systems (HIS) to report healthcare service, and disbursement record from National Health Security Office system. Furthermore, they needed to communicate with people and Covid patients. The participants reported information barriers such as the difficult to use and collapsed central health information system record from Ministry of Public Health, no linkage between health information system, incorrect data, unclear message, Wi-Fi problem. 2.4 Medical products, vaccines & technologies: The hospital adapted medical products, vaccines and technologies system by distribute medical products, accelerating access to vaccines, applied essential medical device, and developing innovations and technologies in health care services. The participants reported barriers to shortage and high price of medical products, medicine, and vaccines due to COVID-19 outbreak, coverage of distribution, and poor-quality. 2.5 Financing: The hospitals used budget of the hospital, special budget, disbursement from NHSO, and donation to fight against Covid-19. The financing barriers addressed unclear disbursement system, and limitation of disbursement. 2.6 leadership and governance: The leaders of team make a good, fast decisions, doing role model of hard work, co-operating, controlling and consulting management team, daring to switch new job, changed mindset, and good governance. However, the participants mentioned about without unity of command as the barriers in Bangkok hospitals. 3. The lessons learned from the management of COVID-19 pandemic in the tertiary health service systems, the key success factors to fight against COVID-19 lies in how to deal with COVID-19, learning and working together, taking advantage of working hard, Thai helping each other, crisis is an opportunity, and academic advising resources in response to COVID-19. 4. Policy synthesis for the tertiary health service systems in COVID-19 pandemic in Bangkok and metropolitan region, given that we now know the importance of revised Incident Command System for Disaster Preparedness with unity of command, developed data information system, and revised stock and allocation system of medical product, should be expected to provide resources to help support health service systems in COVID-19.