Objective. The aim of this Outcome Measures in Rheumatology (OMERACT) Working Group was to determine the core set of outcome domains and subdomains for measuring the effectiveness of shared decision-making (SDM) interventions in rheumatology clinical trials.Methods. Following the OMERACT Filter 2.0, and based on a previous literature review of SDM outcome domains and a nominal group process at OMERACT 2014, (1) an online Delphi survey was conducted to gather feedback on the draft core set and refine its domains and subdomains, and (2) a workshop was held at the OMERACT 2016 meeting to gain consensus on the draft core set. Results.A total of 170 participants completed Round 1 of the Delphi survey, and 116 completed Round 2. Respondents came from 29 countries, with 49% being patients/caregivers. Results showed that 14 out of the 17 subdomains within the 7 domains exceeded the 70% criterion (endorsement ranged from 83% to 100% of respondents). At OMERACT 2016, only 8% of the 96 attendees were patients/caregivers. Despite initial votes of support in breakout groups, there was insufficient comfort about the conceptualization of these 7 domains and 17 subdomains for these to be endorsed at OMERACT 2016 (endorsement ranged from 17% to 68% of participants). Conclusion. Differences between the Delphi survey and consensus meeting may be explained by the manner in which the outcomes were presented, variations in participant characteristics, and the context of voting. Further efforts are needed to address the limited understanding of SDM and its outcomes among OMERACT participants.