To investigate new bone erosion and cartilage destruction predictors in rheumatoid arthritis (RA) patients treated with conventional synthetic disease-modifying antirheumatic drugs (csDMARDs). Placebo-treated patient data from two 12-month, randomized, double-blind, phase 2 (DRIVE) and 3 (DESIRABLE) trials that evaluated denosumab efficacy in csDMARD-treated RA patients were used. Change from baseline in erosion score (ES) of ≥1.0 at 12 months was considered new bone erosion; predictors were identified using a multivariate model. Among 306 patients, mean ± standard deviation disease activity score 28-C-reactive protein (CRP) at baseline was 3.58 ± 1.03. New bone erosion was observed in 90 patients (29.4%). Univariate analysis identified female sex, anti-cyclic citrullinated peptide (CCP) antibody positivity, rheumatoid factor (RF) positivity, tender joint count ≥6, CRP ≥0.3 mg/dL, erythrocyte sedimentation rate (ESR) ≥28 mm/h, and baseline ES ≥3 as significant predictors for new bone erosion. In multivariate analysis, predictors were anti-CCP antibody positivity, CRP ≥0.3 mg/dL, and baseline ES ≥3; RF and ESR were excluded as they strongly correlated with anti-CCP antibody and CRP, respectively. In RA patients treated with csDMARDs, new bone erosion predictors were seropositivity, elevated inflammatory markers, and baseline ES ≥3. DRIVE, JapicCTI-101263; DESIRABLE, NCT01973569