The objective of this study was to assess potential age-related differences in oncologist communication during conversations about adjuvant therapy decisions and subsequent patient decision outcomes. Communication was observed between a cross-section of female patients aged 40 to 80 with early-stage breast cancer (n=180) and their oncologists (n=36) in 14 academic and community oncology practices in two states. Sources of data included audio recordings of visits, followed by post-visit patient interviews. Communication during the visit was assessed using the Siminoff Communication Content and Affect Program. Patient outcome measures included self-reported satisfaction with decision, decision conflict, and decision regret. Results showed that oncologists were significantly more fluent and more direct with older than middle-aged patients and trended toward expressing their own treatment preferences more with older patients. Satisfaction with treatment decisions was highest for women in their 50s and 60s. Decision conflict was significantly associated with more discussion of oncologist treatment preferences and prognosis. Decision regret was significantly associated with patient age and education. Older adults considering adjuvant therapy may find that oncologists' communication accommodations to perceived deficiencies in older adult cognition or communication challenge their decision-making involvement. Oncologists should carefully assess patient decision-making preferences and be mindful of accommodating their speech to age-related stereotypes.