Background Schnitzler syndrome is an adult-onset autoinflammatory disease characterized by urticarial exanthema and monoclonal gammopathy accompanied by systemic symptoms such as fever, bone, and muscle pain. Up to now, approved treatment options are not available. Objective We assessed effects of the anti–IL-1β mAb canakinumab on the clinical signs and symptoms of Schnitzler syndrome. Methods In this phase II, randomized placebo-controlled multicenter study, 20 patients with active disease enrolled in 4 German study centers. Patients were randomly assigned to receive single subcutaneous canakinumab 150 mg or placebo injections for 7 days, followed by a 16-week open-label phase with canakinumab injections on confirmed relapse of symptoms. The primary end point was the proportion of patients with complete clinical response evaluated by physician global assessment at day 7. Key secondary end points included changes in patient-reported disease activity (Schnitzler activity score), inflammation markers (C-reactive protein and serum amyloid A), and quality-of-life assessments (Dermatology Life Quality Index and 36-item short form health survey). Results The proportion of patients with complete clinical response at day 7 was significantly higher ( P  = .001) in the canakinumab-treated group (n = 5 of 7) than in the placebo group (n = 0 of 13). Levels of inflammation markers C-reactive protein and serum amyloid A and quality-of-life scores were significantly reduced in canakinumab-treated but not in placebo-treated individuals. Positive effects continued up to 16 weeks. Adverse events were manageable and included respiratory tract infections, gastrointestinal symptoms, and hypertension. Conclusions In this first placebo-controlled study, canakinumab was effective in patients with Schnitzler syndrome, and thus canakinumab may be further evaluated as a therapeutic option for this rare disease.