Hospital engagement networks (HENs) are part of the largest health care improvement initiative ever undertaken. This article explores whether engagement in improvement activities within a HEN affected quality measures. Data were drawn from 1174 acute care hospitals. A composite quality score was created from 10 targeted topic area measures multiplied by the number of qualifying topics. Scores improved from 5.4 (SD = 6.8) at baseline to 4.6 (5.9) at remeasurement; P < .0001. Hospitals with higher baseline scores demonstrated greater improvement (P < .0001) than hospitals with lower baseline scores. Hospitals with larger Medicaid populations (P = .023) and micropolitan (P = .034) hospitals tended to have greater improvement, whereas hospitals in the West (P = .0009) did not improve as much as hospitals in other regions. After adjusting for hospital characteristics, hospitals with improvement champions (P = .008), a higher level of engagement with their state association (P = .001), and more leadership involvement (P = .005) in HEN demonstrated greater improvement.