Biologic therapy is effective for treatment of moderate-to-severe psoriasis but may be associated with an increased risk for serious infection. To estimate the serious infection rate among patients with psoriasis treated with biologic as compared with nonbiologic systemic agents within a community-based health care delivery setting. We identified 5889 adult Kaiser Permanente Northern California health plan members with psoriasis who had ever been treated with systemic therapies and calculated the incidence rates and 95% confidence intervals (CIs) for serious infections over 29,717 person-years of follow-up. Adjusted hazard ratios (aHRs) were calculated using Cox regression. Adjusting for age, sex, race or ethnicity, and comorbidities revealed a significantly increased risk for overall serious infection among patients treated with biologics as compared with those treated with nonbiologics (aHR, 1.31; 95% CI, 1.02-1.68). More specifically, there was a significantly elevated risk for skin and soft tissue infection (aHR, 1.75; 95% CI, 1.19-2.56) and meningitis (aHR, 9.22; 95% CI, 1.77-48.10) during periods of active biologic use. Risk associated with individual drugs was not examined. We found an increased rate of skin and soft tissue infections among patients with psoriasis treated with biologic agents. There also was a signal suggesting increased risk for meningitis. Clinicians should be aware of these potential adverse events when prescribing biologic agents.