OBJECTIVE: We estimated meaningful change thresholds (MCTs) for Patient-Reported Outcomes Measurement Information System (PROMIS) Fatigue and Pain Interference in rheumatoid arthritis (RA). METHODS: The responsiveness of several patient-reported outcomes (PROs) was assessed among 521 patients with RA in the Arthritis, Rheumatism, and Aging Medical Information Systems (ARAMIS) cohort. PROMIS Fatigue (7-item) and Pain Interference (6-item) short form instruments were administered at baseline, 6 months, and 12 months. Self-reported retrospective changes over the previous 6 months (a lot better/ worse, a little better/worse, stayed the same) were obtained at 6 and 12 months' follow-up. We estimated MCTs using the mean change in PROMIS scores for patients who rated their change "a little better" or "a little worse." RESULTS: Baseline fatigue and pain interference scores were near normal (median 54 and 56, respectively). At 6 months, 7.9% of patients reported their fatigue was a little better compared to baseline (mean change [SD]: -2.6 [4.8]) and 22.8% a little worse (1.7 [5.6]). Pain was a little better for 11.5% of patients (-1.9 [6.1]) and a little worse for 24.2% of patients (0.6 [5.7]). At 12 months, results were similar. Thus, the MCT range was 1-2 points for both fatigue and pain interference. Correlations between change scores and retrospective ratings were low (0.13-0.29), indicating possible underestimation of MCT. CONCLUSION: The group-level MCT for PROMIS Fatigue and Pain Interference is roughly 2-3 points and corresponds to a small effect size, which is consistent with earlier work demonstrating an MCT of 2 points for PROMIS Physical Functioning.