Background Service‐user partnerships in research exist in mental health, but there have been few advances in other disciplines, apart from cancer. Objectives To develop a patient‐generated expectancy measure for new treatments in rheumatoid arthritis (RA), using a participatory method. Method Stage 1: three repeated focus groups and two expert panels with patients with RA conducted by a patient researcher to generate items for the draft questionnaire. Stage 2: feasibility study of draft scale with consecutive outpatient attendees. Results Patients identified 21 dimensions of new treatment expectations, grouped into (i) physical, (ii) psycho‐social and (iii) expectations relating to the impact of treatment. This resulted in a draft instrument assessed in a feasibility study. Discussion and Conclusion The participatory research method was useful in involving patients actively in research and to produce collaboratively a feasible, valid and acceptable measure in RA. The scale will be included in a longitudinal observational study, with newly diagnosed patients, to assess (i) whether the new scale demonstrates sensitivity to change for expectations when receiving new treatment and (ii) participants' completion rate of the new scale compared with five instruments included in the future study.