<p>Cancer-related fatigue (CRF) is a common and debilitating symptom associated with cancer and its treatment. CRF has a detrimental effect on activities of daily living and decreases patients’ quality of life. Developing intervention strategies for managing CRF can be facilitated by identifying factors that are associated with it. Many clinical, demographic, genetic, biological, physical, psychosocial, and behavioral factors have been identified as being associated with CRF. Also, the relationship has been identified between CRF and subjective cognitive functions. Studies have increasingly focused on the association between cognitive dysfunction and CRF in cancer patients. There are numerous processes involved in the development of CRF and cognitive impairment. However, inflammation is a common mechanism that impacts the expression of both symptoms. Consequently, these two symptoms often may co-occur and have a functional relation. Psychoneurological factors, such as CRF, have a crucial role in determining the cognitive functions of cancer patients. Experiencing a CRF level that is higher than average has a detrimental impact on cognitive functions. Impairments in cognitive functions may worsen with increasing CRF severity. Both symptoms have the potential to disrupt activities of daily living, work, and social life. Further research is required to ascertain the association between cognitive dysfunction and CRF, particularly emphasizing the cognitive functions more significantly affected by increasing CRF levels. The purpose of this article is to review fatigue in cancer patients and the associated factors, with particular emphasis on the relationship between cognitive dysfunction and CRF.</p>