Background: Little data exist on perceptions of guideline-based care in oncology. This qualitative analysis describes patients’ and oncologists’ views on the value of guideline-based care as well as discussing guidelines when making metastatic breast cancer (MBC) treatment decisions. Patients and methods: In-person interviews completed with MBC patients and community oncologists and focus groups with academic oncologists were audio-recorded and transcribed. Two coders utilized a content analysis approach to analyze transcripts independently using NVivo. Major themes and exemplary quotes were extracted. Results: Participants included 20 MBC patients, 6 community oncologists, and 5 academic oncologists. Most patients were unfamiliar with the term “guidelines.” All patients desired to know if they were receiving guideline-discordant treatment but were often willing to accept this treatment. Five themes emerged explaining this including trusting the oncologist, relying on the oncologist’s experiences, being informed of rationale for deviation, personalized treatment, and openness to novel therapies. Physician discussions regarding the importance of guidelines revealed three themes: consistency with scientific evidence, insurance coverage, and limiting unusual practices. Oncologists identified three major limitations in using guidelines: lack of consensus, inability to “think outside the box” to personalize treatment, and lack of guideline timeliness. Although some oncologists discussed guidelines, it was often not considered a priority. Conclusions: Patients expressed a desire to know whether they were receiving guideline-based care but were amenable to guideline-discordant treatment if the rationale was made clear. Providers’ preference to limit discussions of guidelines is discordant with patients’ desire for this information and may limit shared decision-making.