OBJECTIVE: To evaluate whether the risks of herpes zoster (HZ) differed by biologic agents with different mechanisms of action (MOAs) in older rheumatoid arthritis (RA) patients. METHODS: Using Medicare data from 2006-2011, among RA patients with prior biologic agent use and no history of cancer or other autoimmune diseases, this retrospective cohort study identified new treatment episodes of abatacept, adalimumab, certolizumab, etanercept, golimumab, infliximab, rituximab, and tocilizumab. Followup started on initiation of the new biologic agent and ended at any of the following: first incidence of HZ, a 30-day gap in current exposure, death, a diagnosis of other autoimmune disease or cancer, loss of insurance coverage, or December 31, 2011. We calculated the proportion of RA patients vaccinated for HZ in each calendar year prior to biologic agent initiation and HZ incidence rate for each biologic agent. We compared HZ risks among therapies using Cox regression adjusted for potential confounders. RESULTS: Of 29,129 new biologic treatment episodes, 28.7% used abatacept, 15.9% adalimumab, 14.8% rituximab, 12.4% infliximab, 12.2% etanercept, 6.1% tocilizumab, 5.8% certolizumab, and 4.4% golimumab. The proportion of RA patients vaccinated for HZ prior to biologic agent initiation ranged from 0.4% in 2007 to 4.1% in 2011. We identified 423 HZ diagnoses with the highest HZ incidence rate for certolizumab (2.45 per 100 person-years) and the lowest for golimumab (1.61 per 100 person-years). Neither the crude incidence rate nor the adjusted hazard ratio differed significantly among biologic agents. Glucocorticoid use had a significant association with HZ. CONCLUSION: Among older patients with RA, the HZ risk was similar across biologic agents, including those with different MOAs.