Aims Australia’s Royal Commission into Aged Care Quality and Safety emphasised the importance of co-design in aged care research. However, co-design is rarely evaluated, limiting understanding of how people who live in aged care experience involvement in these processes and whether they contribute to improved services. We explored researchers’ experiences of evaluating co-design in residential aged care. Methods Cross-sectional survey of researchers who have undertaken co-design in residential aged care. Pilot-tested survey items were informed by a prior scoping review and co-design evaluation frameworks, and included multiple-choice, Likert-type, ranking, and open-ended formats. Recruitment occurred via direct invitation, advertisement and dissemination through professional networks. The survey could be forwarded by recipients to colleagues to maximise reach. Results Fifty-one responses were received, with forty-one meeting inclusion criteria. Representation spanned eight countries, predominantly Australia (41%) and the United Kingdom (34%). Most respondents (90%) agreed that evaluation of co-design processes is important. Qualitative approaches were most commonly used, however there was limited use of evaluation frameworks or theory. Common barriers preventing evaluation included resident frailty (n=11) and resource constraints (time/funding) (n=10). Conclusions Despite widespread enthusiasm for co-design in aged care, the emphasis appears to be on ‘doing’ co-design rather than understanding its impact. Evaluation of co-design involving aged care residents is not universal practice, although most researchers agree it’s important. Without evaluation, co-design risks becoming a widely adopted practice, with value and impact being assumed rather than demonstrated.