Background <p>The newly discovered Treg subset (CLA⁺ Tregs) expressing cutaneous lymphocyte-associated antigen is associated with inflammatory conditions. This study elucidated the role of CLA⁺ Tregs in rheumatoid arthritis (RA) development and its responses to treatment.</p> Methods <p>A total of 12 T cell subsets, together with total T cells, B cells, and NK cells were analyzed in 169 patients with RA and 114 healthy controls using flow cytometry. Autoantibodies were detected by ELISA. The logistic regression models were employed to assess the association between cell subsets and rheumatoid arthritis. Relationships between CLA⁺ Tregs and clinical variables were assessed.</p> Results <p>Among the immune cell subsets analyzed, CLA⁺ Tregs were the most significantly reduced ones in patients with RA compared with healthy controls (OR 0.825 [0.764–0.891], <i>p</i> &lt; 0.001). Decreased CLA⁺ Tregs were strongly correlated to active disease status (adjusted OR 0.814 [0.733–0.902], <i>p</i> = 0.004; AUC 0.916 [0.869–0.963], <i>p</i> &lt; 0.001). Decreased CLA⁺ Tregs were associated with higher swollen joint count, tender joint count and DAS28 scores, as well as systemic involvements, including interstitial lung disease (ILD), anemia, fever, and skin vasculitis. Additionally, rheumatoid factor (RF) and anti-mutated citrullinated vimentin antibody (anti-MCV) were correlated to lower CLA⁺ Tregs. Compared to baseline prior treatment, CLA⁺ Tregs increased significantly in RA patients, accompanied by improvements in disease activity (median, 9.60% vs. 18.80%, <i>p</i> = 0.044; 3.41 cells/µL vs. 7.86 cells/µL, <i>p</i> = 0.011, respectively).</p> Conclusions <p>The results demonstrated a significant reduction of CLA⁺ Tregs in active RA, especially in patients with systemic damages. Recovery of CLA⁺ Tregs may predict therapeutic responses.</p>