PurposeTo empirically assign severity levels (e.g.,mild,moderate) to four relatively new patient-reported outcome measures (PROMs) for adults with acquired cognitive/language disorders. They include the Communicative Participation Item Bank, the Aphasia Communication Outcome Measure, and Neuro-QoL’s item banks of Cognitive Function (v2.0) and Ability to Participate in Social Roles and Activities (v1.0).MethodWe conducted 17 focus groups that comprised 22 adults with an acquired cognitive/language disorder from stroke, Parkinson’s disease, or traumatic brain injury; 30 care partners of an adult with an acquired cognitive/language disorder; and 42 speech-language pathologists who had experience assessing/treating individuals with those and other cognitive/language disorders. In a small, moderated focus-group format, participants completed “PROM-bookmarking” procedures: They discussed hypothetical vignettes based on PROM item responses about people with cognitive/language disorders and had to reach consensus regarding whether their symptoms/function should be categorized aswithin normal limitsormild,moderate, orseverechallenges.ResultsThere was generally good agreement among the stakeholder groups about how to classify vignettes, particularly when they reflected very high or low functioning. People with aphasia described a larger range of functional communication challenges as “mild” compared to other stakeholder types. Based on a consensus across groups, we present severity levels for specific score ranges for each PROM.ConclusionStandardized, stakeholder-informed severity levels that aid interpretation of PROM scores can help clinicians and researchers derive better clinical meaning from those scores, for example, by identifying important clinical windows of opportunity and assessing when symptoms have returned to a “normal” range.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11136-022-03337-2.