Background: Multiple treatments with similar efficacy exist for mPC, leaving patients (pts) with complicated treatment choices. Shared decision-making (SDM) can facilitate treatment decisions. The extent to which SDM is used in mPC is unknown. We assessed mPC pt, caregiver, and physician perceptions of decision locus of control (DLOC) (SDM vs. physician- or pt-directed decisions), and the degree of agreement between groups. Methods: Pt/caregiver/physician triads completed surveys of decision-making practices between 12/2016 and 11/2017 after a clinic visit in which a decision occurred. Pts were included only if they had a caregiver present. To evaluate the degree of agreement between pt, caregiver, and physician perceptions of DLOC, we used the quadratic-weighted kappa coefficient (κ). Agreement was evaluated on an overall basis and by pt age group (5-year increments). Results: 50 pt/caregiver/physician triads participated, with median pt age of 72 yo. Most pts were white (96%) and married (90%). A majority of pts, caregivers, and physicians reported SDM (66%, 56%, and 52%, respectively). No group reported completely pt-directed decisions. Pts and physicians demonstrated agreement about DLOC for most encounters (weighted κ = 0.35; P = 0.01). Overall, pts and physicians agreed on the DLOC in 44% of cases, and SDM was the most common agreed-upon DLOC (36%). Relative to physicians, 34% of pts reported more pt influence on DLOC, and 22% of pts reported less pt influence on DLOC. In contrast, caregiver reports of DLOC were independent of physician reports (weighted κ = 0.23; P = 0.55). Overall, caregivers and physicians agreed on DLOC in 38% of cases, and SDM was the most common agreed-upon DLOC (32%). Relative to physicians, 46% of caregivers reported more pt influence on DLOC and 16% of caregivers reported less pt influence on DLOC. There was a statistically significant difference in the degree of agreement by pt age group between pts and physicians (P = 0.045) and caregivers and physicians (P = 0.002), although no specific pattern according to pt age was noted. Conclusions: A majority of pts, caregivers, and physicians reported SDM occurring in routine clinical visits for mPC. Pts reported a higher degree of agreement with their physicians in DLOC than caregivers. Both pts and caregivers perceived greater pt influence on treatment choice than physicians. Efforts to explore the association between SDM, pt satisfaction, and quality of life are ongoing.