Purpose: This study analyzed recent trends of instrument usage assessing cognitive function of breast cancer patients undergoing chemotherapy. Methods: The researcher collected 64 studies outside the country that were published between January 1996 and August 2010. Results: There was no study on the instrument assessing all domains of cognitive function in breast cancer patients undergoing chemotherapy. Most instruments assessing cognitive function of breast cancer patients have been used for patients with dementia, depression, and/or organic brain damage. Also the objective neuropsychological tests such as the grooved pegboard for the psychomotor area, RCFT copy in visuospatial skill area and the WAIS-III block design have low sensitivity for measuring cognitive function in breast cancer patients, thus they are not good for applying to breast cancer patients. Conclusion: There is a need to develop an instrument which has good sensitivity and specificity for measuring the cognitive function of the breast cancer patients who experienced cognitive impairment after chemotherapy treatment. In addition, the developed instrument needs to be accessible and feasible in any nursing clinical setting for the purpose of accurate assessment and evaluation of the cognitive function among breast cancer patients.