Management of older breast cancer patients is challenging due to a lack of good quality evidence regarding the role of adjuvant chemotherapy. Older women can benefit as much from adjuvant chemotherapy as younger women, although they have an increased risk of toxicities. Decisions regarding adjuvant chemotherapy should be made based on tumor biology and biological age, rather than chronological age. Geriatrician assessment can detect subtle functional deficits that may impact on the ability of the patient to tolerate chemotherapy; however, implementation of comprehensive geriatric assessment in the oncology setting is challenging. Instead, numerous frailty screening tools are in development. Future advances should incorporate more accurate and efficient means for determining the biological age of elderly breast cancer patients, which will better define the risk:benefit ratio of adjuvant chemotherapy.