Objective.To reach consensus on the core domains to be included in a core domain set for clinical trials of shoulder disorders using the Outcome Measures in Rheumatology (OMERACT) Filter 2.1 Core Domain Set process.Methods.At OMERACT 2018, the OMERACT Shoulder Working Group conducted a workshop that presented the OMERACT 2016 preliminary core domain set and its rationale based upon a systematic review of domains measured in shoulder trials and international Delphi sessions involving patients, clinicians, and researchers, as well as a new systematic review of qualitative studies on the experiences of people with shoulder disorders. After discussions in breakout groups, the OMERACT core domain set for clinical trials of shoulder disorders was presented for endorsement by OMERACT 2018 participants.Results.The qualitative review (n = 8) identified all domains included in the preliminary core set. An additional domain, cognitive dysfunction, was also identified, but confidence that this represents a core domain was very low. The core domain set that was endorsed by the OMERACT participants, with 71% agreement, includes 4 “mandatory” trial domains: pain, function, patient global — shoulder, and adverse events including death; and 4 “important but optional” domains: participation (recreation/work), sleep, emotional well-being, and condition-specific pathophysiological manifestations. Cognitive dysfunction was voted out of the core domain set.Conclusion.OMERACT 2018 delegates endorsed a core domain set for clinical trials of shoulder disorders. The next step includes identification of a core outcome measurement set that passes the OMERACT 2.1 Filter for measuring each domain.