ObjectiveAssess acceptability, appropriateness and feasibility of the Practical Guide to Implementing patient-reported outcome measures (PROMs) in Gender-Affirming Care (PG-PROM-GAC) from a sample of patients and healthcare professionals.DesignCross-sectional study conducted August–October 2023.SettingParticipants were recruited from a National Health Service (NHS) gender clinic.ParticipantsPatient participants seeking care and healthcare professionals working at an NHS gender clinic were eligible for participation. The PG-PROM-GAC was sent to participants via email for review.Outcome measuresThree validated tools to measure acceptability, appropriateness and feasibility were administered: the acceptability of intervention measure (AIM), intervention appropriateness measure (IAM) and feasibility of intervention measure (FIM). The percentage of participants indicating agreement or disagreement with items on the AIM, IAM and FIM was calculated.ResultsA total of 132 transgender and gender diverse (TGD) patients (mean age, SD: 33, 14) and 13 gender-affirming healthcare professionals (mean age, SD: 43, 11) completed the AIM, IAM and FIM, representing a range of gender identities. The cumulative percentage of patients indicating agree or strongly agree on the AIM, IAM and FIM for the patient-relevant strategies in the PG-PROM-GAC was over 50% for each item. The cumulative percentage of patients indicating disagree or strongly disagree on the AIM, IAM and FIM for the PG-PROM-GAC was less than 20% for each item. The cumulative percentage of healthcare professionals indicating agree or strongly agree on the AIM, IAM and FIM for the healthcare professional-relevant strategies in the PG-PROM-GAC was over 38% for each item. The cumulative percentage of healthcare professionals indicating disagree or strongly disagree on the AIM, IAM and FIM for the PG-PROM-GAC was less than 15% for each item.ConclusionsGender-affirming healthcare professionals and TGD patients find the PG-PROM-GAC acceptable, appropriate and feasible. The PG-PROM-GAC is ready-to-use for clinicians, policy-makers and researchers committed to service improvement for gender-affirming care.