Adequate assessment of cancer-related cognitive impairment (CRCI) refers to outcomes among the many options of objective (performance-based) and subjective (perceived-based) cognitive assessments. Internationally recommended objective tools like neuropsychological tests (NPTs) have been standardized, and normative data for interpreting the results have also been published. Although the use of objective cognitive assessments like patient-reported outcomes (PROs) is encouraged, PROs’ results are influenced by the psychological and functional states of co-occurring symptoms. Neuroimaging devices have recently been used as evaluation methods to supplement the results of NPTs and PROs. The aims of this review were to highlight internationally standardized NPTs and PROs and to summarize assessment methods for comprehensive cognitive function assessment. This chapter further discusses the factors that must be considered for proper CRCI assessment and the various mechanisms that may underlie these relationships.