Background: The number of clinical trials conducted in Korea continues to increase and an increasing proportion focus on severe and rare incurable diseases. After the start of the severe acute respiratory syndrome, coronavirus disease 2019 (COVID-19), Korea Centers for Disease Control and Prevention (KCDC) developed guidelines to prevent the spread of infection. This study evaluated the impact of COVID-19 and the KCDC guideline on the conduct of clinical research in Korea. The purpose was to develop recommendations on how to minimize the risk of infection while enabling subjects to take part in the trials if no better alternative treatment options were available. Methods: The impact on subject's scheduled visits and major milestones of clinical trials in Korea were measured by conducting a survey among clinical project manager (CPMs) working at global clinical research organization. The policy on monitor's access to hospital and site initiation meetings was investigated through correspondence with clinical trial center of 39 hospitals. The Top 25 pharmaceutical companies' official press and public clinical trial registry database were used to analyze companies' trial strategy during the pandemic and COVID-19 clinical research status, respectively. Results: Of 85 CPMs, 12% reported that trial subjects' scheduled visits had been affected in their project. Monitors' access to hospital for source data verification was restricted at all sites in February 2020. Accordingly, 43% of 105 CPMs reported that the COVID-19 epidemic had an effect on study major milestones and data cleaning and database lock accounted for > 60% of milestones affected. In addition, 87% sites advised not to have site initiation meetings and 52% pharmaceutical companies suspended recruitment or new study start- up due to the pandemic. On the other hands, the number of COVID-19 related clinical trials increased rapidly in Korea and worldwide, with investigator-initiated trials accounting for 47% and 63% of all trials locally and globally, respectively. Most trials were phase 2 and were in the recruitment stage. Conclusion: The COVID-19 and the KCDC guideline influenced all parties involved in clinical trials in Korea. In order to ensure the safety and well-being of trial subjects during the pandemic, new approaches are required for clinical trials to respond to the impact actively. Method of non-contact is developed to replace and supplement the face-to-face contact and alternatives to reduce the travel is introduced to decrease the risk of infection for all trial participants in whole trial process. The relevant regulations should be developed and the guidelines for foreign countries need to be adopted in accordance with the situation in Korea. COVID-19 trial is rapidly increasing worldwide and continuous support of health authorities, regulation, and facilities is required for developing the treatments with protecting all trial participants.