Background: Women with metastatic breast cancer (MBC) face numerous treatment and ACP decisions along their illness trajectory. We aimed to explore the treatment and ACP decision-making processes and decision support needs of women with MBC. Methods: Convergent, parallel mixed methods study (9/08-7/09). Sample included women with MBC managed by 3 breast oncologists at the Norris Cotton Cancer Center, Lebanon, NH. Participants completed a semi-structured interview and standardized decision-making instruments (decision control preferences) at study enrollment (T1; n = 22) and when they faced a decision point or 3 months later (T2; n = 19), whichever came first. Results: Participants (n = 22) where all white, averaged 62 years and were mostly married (54%), retired (45%), had a ≥ bachelor’s degree (45%), and had incomes > $40,000 (50%). On the control preferences scale, most women reported a preference for a ‘shared decision’ with clinician (T1 = 14 (64%) vs T2 = 9 (47%)) compared to making the decision themselves (T1 = 6 (27%) vs T2 = 6 (32%)), or delegating the decision to their doctor (T1 = 2 (9%) vs T2 = 4 (21%)). In semi-structured interviews about their actual treatment decision-making experience, women described experiencing a passive or delegated rather than a shared decision-making process. Conversely, women described a much more active ACP decision-making process that was often shared with family rather than their oncologists. Conclusions: Women selected a “shared” process using a validated tool; however their descriptions of the treatment decision-making processes were inconsistent with their actual experience, which was a more passive process in which they followed the oncologists’ treatment suggestions.