OBJECTIVE: To compare the effects a Mediterranean diet (MedDiet) versus the Irish Healthy Eating Guidelines (HEG) on physical function and quality of life in adults with rheumatoid arthritis (RA) in Ireland. METHODS: Forty-four adults with RA were randomised (1:1) to the MedDiet or HEG for 12 weeks. The intervention included three video teleconsultations and two follow-up telephone calls facilitated by a Registered Dietitian (RD). Changes in physical function by Health Assessment Questionnaire- Disability Index (HAQ-DI) and quality of life by Rheumatoid Arthritis Quality of Life Questionnaire (RAQoL) were the primary outcomes measured. Secondary outcomes included changes in dietary adherence, physical activity by Yale Physical Activity survey (YPAS), patient-perceived pain and general health, and anthropometric measures. All measurements were administered at baseline and repeated at 6 and 12 weeks. RESULTS: Forty participants completed the study. Participants were primarily females (87.5%), mean age was 47.5 ± 10.9 years. At the end of the intervention, participants in the MedDiet group reported significantly better physical function (p = 0.006) and quality of life (p = 0.037) compared to HEG group. From baseline to 12 weeks, physical function significantly improved in both diet groups, MedDiet (0.9 ± 0.5 to 0.5 ± 0.4 units, p < 0.001) and HEG (1.4 ± 0.7 to 1.0 ± 0.6 units, p < 0.001). Quality of life also significantly improved in the MedDiet (10.1 ± 7.5 to 4.0 ± 4.7 units, p < 0.001) and HEG group (11.25 ± 7.2 to 7.9 ± 6.4 units, p = 0.048). Physical activity improved significantly in the MedDiet (56.7 ± 28.6 to 70.6 ± 33.5 points, p = 0.01) but not within the HEG group despite similar recommendations. CONCLUSION: Adhering to the MedDiet and Irish Healthy Eating Guidelines resulted in improvements in RA patient-reported outcomes. The changes observed in both diet groups are likely due to the improvement in overall diet quality irrespective of dietary prescription. TRIAL REGISTRATION NUMBER: NCT04262505.