Abstract Objective To determine the effect of a multidisciplinary lifestyle program in patients with RA with low–moderate disease activity. Methods In the ‘Plants for Joints’ (PFJ) parallel-arm, assessor-blind randomized controlled trial, patients with RA and 28-joint DAS (DAS28) ≥2.6 and ≤5.1 were randomized to the PFJ or control group. The PFJ group followed a 16-week lifestyle program based on a whole-food plant-based diet, physical activity and stress management. The control group received usual care. Medication was kept stable 3 months before and during the trial whenever possible. We hypothesized that PFJ would lower disease activity (DAS28). Secondary outcomes included anthropometric, metabolic and patient-reported measures. An intention-to-treat analysis with a linear mixed model adjusted for baseline values was used to analyse between-group differences. Results Of the 83 people randomized, 77 completed the study. Participants were 92% female with mean (s.d.) age of 55 (12) years, BMI of 26 (4) kg/m2 and mean DAS28 of 3.8 (0.7). After 16 weeks the PFJ group had a mean 0.9-point greater improvement of DAS28 vs the control group (95% CI 0.4, 1.3; P < 0.0001). The PFJ intervention led to greater decreases in body weight (difference –3.9 kg), fat mass (–2.8 kg), waist circumference (–3 cm), HbA1c (–1.3 mmol/mol) and low-density lipoprotein (–0.32 mmol/l), whereas patient-reported outcome measures, blood pressure, glucose and other lipids did not change. Conclusion The 16-week PFJ multidisciplinary lifestyle program substantially decreased disease activity and improved metabolic status in people with RA with low–moderate disease activity. Trial Registration International Clinical Trials Registry Platform; https://www.who.int/clinical-trials-registry-platform; NL7800.