Purpose: The purpose of this study was to investigate the factors affecting the quality of life of cancer patients by examining the de-gree of the COVID-19 pandemic-related depression, anxiety, stress, and treatment-crisis. Methods: Data were collected from 132 cancer patients undergoing surgery, chemotherapy, radiotherapy, and hormone therapy at K University Hospital in D City using a structured questionnaire. The period of data collection was from May 6 to May 28, 2022. The collected data were analyzed using de-scriptive statistics, t-test, ANOVA, Pearson's correlation, and stepwise multiple regression. Results: The mean scores of quality of life, depression, anxiety, stress, and treatment-crisis during the COVID-19 pandemic were 84.64 +/- 29.09, 15.14 +/- 6.49, 4.66 +/- 5.27, 75.83 +/- 17.70, and 78.52 +/- 19.95, respectively. In terms of factors affecting the quality of life related to the COVID-19 pandemic, CO-VID-19 pandemic-related stress (beta=.41,p<.001) appeared to have the greatest impact, followed by COVID-19 pandemic-related treatment-crisis (beta=.28,p=.002), anxiety (beta=.21, p=.002), and gender (beta=.14, p=.009), with a total explanatory power of 67.6%. Con-clusion: To improve the quality of life during the COVID-19 pandemic, COVID-19 pandemic-related stress, treatment-crisis, and anxiety should be periodically monitored and nursing interventions such as education on infection prevention, management, and emotional support programs should be provided to decrease the COVID-19 pandemic-related stress, treatment-crisis, and anxiety.