Importance: Few treatments are available for patients with glucocorticoid-dependent polymyalgia rheumatica. IL-6 antagonists may reduce disease activity in patients with active glucocorticoid-dependent polymyalgia rheumatica. Objective: To compare the efficacy of tocilizumab vs placebo in patients with glucocorticoid-dependent polymyalgia rheumatica. Design, setting, and participants: This double-blind, parallel-group, placebo-controlled randomized clinical trial enrolled 101 patients with polymyalgia rheumatica at 17 hospitals in France from February 2017 to October 2019. Final follow-up occurred in November 2020. Inclusion criteria were persistent disease activity (polymyalgia rheumatica activity score computed using the C-reactive protein level [CRP PMR-AS] >10) and prednisone dose greater than or equal to 10 mg per day. Interventions: Patients were randomly assigned to receive intravenous tocilizumab (8 mg/kg; n = 51) or placebo (n = 50) every 4 weeks for 24 weeks, combined with predefined standardized tapering of oral prednisone. Main outcomes and measures: The primary efficacy end point was CRP PMR-AS less than 10 (range, 0-100; higher values indicate greater activity; no minimal clinically important difference defined) combined with either prednisone dose less than or equal to 5 mg per day or a decrease in prednisone dose greater than or equal to 10 mg from baseline at week 24. There were 11 secondary outcomes assessed at week 24 included in this report, including disease activity (measured by CRP PMR-AS) and the proportion of patients no longer taking prednisone. Results: Of the 101 randomized patients (mean age, 67.2 years; 68 [67.3%] women), 100 (99%) received at least 1 infusion and 100 completed the trial. The primary end point was achieved in 67.3% of patients in the tocilizumab group and 31.4% of patients in the placebo group (adjusted difference, 36.0% [95% CI, 19.4%-52.6%]; adjusted relative risk, 2.3 [95% CI, 1.5-3.6]; P < .001). Of 11 reported secondary end points at 24 weeks, 7 showed significant differences favoring tocilizumab, including mean CRP PMR-AS score (7.5 [95% CI, 5.4-9.6] vs 14.9 [95% CI, 11.4-18.4]; adjusted difference, -7.5 [95% CI, -11.2 to -3.8]; P < .001) and the percentage of patients no longer receiving prednisone (49.0% vs 19.6%; adjusted difference, 29.3% [95% CI, 18.9%-39.7%]; adjusted relative risk, 2.5 [95% CI, 1.8-3.5]; P < .001). The most frequent adverse events were infections, experienced by 23 patients (46.9%) in the tocilizumab group and 20 (39.2%) in the placebo group. Conclusions and relevance: Among patients with active polymyalgia rheumatica despite prednisone therapy, tocilizumab, compared with placebo, resulted in a significantly greater percentage of patients with a CRP PMR-AS less than 10 with reduced prednisone requirements at week 24. Further research is needed to confirm efficacy and to determine the balance of potential benefits and harms.