Cancer is a disease that affects various aspects of patients' lives. The COVID-19 pandemic has presented numerous challenges and difficulties for cancer patients, exacerbating their already vulnerable conditions. Identifying the challenges these patients face can be a practical step toward improving their quality of care in future pandemics. This qualitative study aims to identify the challenges cancer patients encounter during the COVID-19 pandemic. This is a qualitative study with a content analysis approach. Participants included 16 cancer patients hospitalized at Tabriz Shahid Ghazi Hospital in 2020. Sampling was conducted purposefully, and interviews were continued until data saturation was achieved. All interviews were recorded and transcribed at the earliest opportunity. The data were analyzed using content analysis based on the Lundman and Graneheim method. Data analysis led to the identification of four categories of challenges faced by cancer patients during the pandemic: Mental derangement and fear (fear of premature death, fear of contracting COVID-19, fear of disease recurrence), ineffective nurse-patient communication (personal protective equipment and distant care from nursing stations), economic instability (difficulties in providing for the family's livelihood and increased medical expenses), and reduced access to services (Contracting of infection among doctors and nurses and redirection of resources and services to COVID-19 patients). Participants expressed that these challenges were additional to their pre-existing difficulties and were intensified by the COVID-19 pandemic. Team support and interdisciplinary collaboration can be beneficial in addressing mental derangement and severe fears and solving problems comprehensively. Using various methods to facilitate safe and continuous communication between nurses and patients aside from their beds can give patients a greater sense of calmness. Financial facilitations can alleviate pressure on patients, and planning and communication strategies for accessing care and treatment services during a pandemic should be organized in advance.