Objective: To report the 2-year efficacy and safety of tocilizumab (TCZ) in patients with polyarticular-course juvenile idiopathic arthritis (JIA). Methods: Patients ages 2–17 years with active polyarticular-course JIA, in whom treatment with methotrexate was unsuccessful, received 16 weeks of open-label intravenous TCZ in part 1 (once every 4 weeks: 8 mg/kg or 10 mg/kg for body weight [BW] <30 kg; 8 mg/kg for BW ≥30 kg). Assessments were based on the JIA–American College of Rheumatology (ACR) response (defined as percentage of improvement in ≥3 of the 6 JIA core response variables [CRVs]). Patients with at least a JIA-ACR30 response (defined as ≥30% improvement in ≥3 of the 6 JIA CRVs without worsening in >1 of the remaining JIA CRVs by >30%) at week 16 were randomly assigned (1:1) to receive TCZ or placebo in part 2. Patients remained in part 2 until either week 40 or the occurrence of JIA flare. Upon starting part 3, all patients received open-label TCZ. At week 104 of the study, efficacy was assessed using JIA-ACR50/70/90 response rates (defined as 50%, 70%, or 90% improvement, respectively), achievement of inactive disease, and the Juvenile Arthritis Disease Activity Score in 71 joints (JADAS-71). Safety was assessed in the all-exposure population per 100 patient-years of exposure. Results: Overall, 188 patients entered part 1, 166 patients entered part 2, and 160 patients entered part 3. By week 104, among the 188 patients in the modified intent-to-treat group who received TCZ, JIA-ACR50/70/90 response rates were 80.3%/77.1%/59.6%, respectively, the median JADAS-71 score decreased from 3.6 at week 40 to 0.7 at week 104, 51.1% of patients had achieved inactive disease, and 31 of 66 patients who had been receiving glucocorticoids discontinued them. Adverse event (AE) and serious AE rates were 406.5 per 100 patient-years and 11.1 per 100 patient-years, respectively. The infection rate was 151.4 per 100 patient-years, and the serious infection rate was 5.2 per 100 patient-years. Conclusion: Patients treated with TCZ for polyarticular-course JIA showed high-level disease control for up to 2 years. The TCZ safety profile was consistent with that previously reported.