IMPORTANCE: The death of a pediatric patient with sepsis motivated New York to mandate statewide sepsis treatment in 2013. The mandate included a 1-hour bundle of blood cultures, broad-spectrum antibiotics, and a 20-mL/kg intravenous fluid bolus. Whether completing the bundle elements within 1 hour improves outcomes is unclear. OBJECTIVE: To determine the risk-adjusted association between completing the 1-hour pediatric sepsis bundle and individual bundle elements with in-hospital mortality. DESIGN, SETTINGS, AND PARTICIPANTS: Statewide cohort study conducted from April 1, 2014, to December 31, 2016, in emergency departments, inpatient units, and intensive care units across New York State. A total of 1179 patients aged 18 years and younger with sepsis and septic shock reported to the New York State Department of Health who had a sepsis protocol initiated were included. EXPOSURES: Completion of a 1-hour sepsis bundle within 1 hour compared with not completing the 1-hour sepsis bundle within 1 hour. MAIN OUTCOMES AND MEASURES: Risk-adjusted in-hospital mortality. RESULTS: Of 1179 patients with sepsis reported at 54 hospitals (mean SD age, 7.2 6.2 years; male, 54.2%; previously healthy, 44.5%; diagnosed as having shock, 68.8%), 139 (11.8%) died. The entire sepsis bundle was completed in 1 hour in 294 patients (24.9%). Antibiotics were administered to 798 patients (67.7%), blood cultures were obtained in 740 patients (62.8%), and the fluid bolus was completed in 548 patients (46.5%) within 1 hour. Completion of the entire bundle within 1 hour was associated with lower risk-adjusted odds of in-hospital mortality (odds ratio OR, 0.59 95% CI, 0.38 to 0.93, P = .02; predicted risk difference RD, 4.0% 95% CI, 0.9% to 7.0%). However, completion of each individual bundle element within 1 hour was not significantly associated with lower risk-adjusted mortality (blood culture: OR, 0.73 95% CI, 0.51 to 1.06, P = .10; RD, 2.6% 95% CI, −0.5% to 5.7%; antibiotics: OR, 0.78 95% CI, 0.55 to 1.12, P = .18; RD, 2.1% 95% CI, −1.1% to 5.2%, and fluid bolus: OR, 0.88 95% CI, 0.56 to 1.37, P = .56; RD, 1.1% 95% CI, −2.6% to 4.8%). CONCLUSIONS AND RELEVANCE: In New York State following a mandate for sepsis care, completion of a sepsis bundle within 1 hour compared with not completing the 1-hour sepsis bundle within 1 hour was associated with lower risk-adjusted in-hospital mortality among patients with pediatric sepsis and septic shock.