Purpose: Patients with cancer experience psychological and social problems; in particular, older patients with cancer face many difficulties during the cancer treatment process owing to aging and underlying diseases. Furthermore, the lives of individuals may be impacted by the COVID-19 pandemic. Therefore, the purpose of this study is to describe the experiences of older patients with cancer during the cancer diagnosis and treatment process amid the COVID-19 pandemic. Methods: This study employed a qualitative, descriptive phenomenological approach to explore and analyze the experiences of the participants. The participants in this study consisted of patients aged over 65 who were diagnosed with cancer, and data were collected from May 4 to June 30, 2022 through in-depth individual interviews. The collected data were analyzed using Giorgi’s phenomenological analysis. Results: Participants were six older patients with cancer with an average age of 69.66 years. Five theme clusters and 15 themes were generated. The theme clusters were “psychological adaptation to cancer diagnosis,” “receiving social and medical support,” “difficulty in the treatment process,” “fear of the COVID-19 pandemic,” and “living through difficulties.” Conclusion: This study revealed that older patients with cancer demonstrated a unique psychology about how to accept the shock of the diagnosis and the resulting coping patterns and feelings of depression. Additionally, it was verified that older patients with cancer, susceptible to infections due to their advanced age and weakened immunity, also face an increased vulnerability to COVID-19. Therefore, a support system tailored to the characteristics of older patients with cancer should be established.