The aim of this study was to investigate the association between body-mass index (BMI) and remission in RA patients receiving conventional synthetic (cs-) or the biological Disease-Modifying Antirheumatic Drug (DMARD), tocilizumab. Individual participant data (IPD) were pooled from five trials investigating tocilizumab and/or csDMARDs therapy (primarily methotrexate) for RA. Time to first remission was recorded according to the Simplified Disease Activity Index (SDAI) and Clinical Disease Activity Index (CDAI). BMI was classified according to WHO definitions. Associations between baseline BMI and remission were assessed by Cox-proportional hazard analysis. IPD were available from 5428 patients treated with tocilizumab ± csDMARDs (n = 4098) or csDMARDs alone (n = 1330). Of these, 1839 (33.9%) had normal BMI, 1780 (32.8%) overweight, 1652 (30.4%) obese and 157 (2.9%) were underweight. Obesity, compared to normal BMI, was associated with less frequent remission using SDAI (adjusted HR 0.80 [95% CI 0.70–0.92]) and CDAI (adjusted HR 0.77 [0.68–0.87]). As continuous variable, increased BMI was associated with less frequent SDAI (P = 0.001) and CDAI (P = 0.001) defined remission. No heterogeneity in identified associations was observed between studies (P = 0.08) or treatments (P = 0.22). Obesity was negatively associated with RA disease remission regardless of RA therapy, suggesting that baseline BMI should be considered as a stratification factor in future RA trials.