Background: Clostridioides difficile infection (CDI) is on the rise. Objective: To evaluate the effect of a tiered, evidence-based intervention to prevent CDI. Design: Pre-post observational evaluation of a prospective, 12-month, national, nonrandomized, clustered quality improvement project to reduce hospital health care-associated infection. Setting: Acute care, long-term acute care, and critical access hospitals working with state partner organizations (state hospital associations and state health departments) to improve health care-associated infection prevention practices. Participants: Targeted hospitals had a high burden of CDI and another health care-associated infection. Other hospitals that did not meet these criteria volunteered to participate. Intervention: Multimodal intervention that consisted of 1) on-demand educational modules and webinars, 2) in-person meetings facilitated by state-level partners, 3) feedback and recommendations for implementation of evidence-based recommendations (including a CDI-specific guide on which interventions to implement), and 4) guided facilitation through infection prevention resources and site visits. Measurements: Pre- and postintervention CDI rates. Results: Between November 2016 and May 2018, 387 hospitals (366 of which reported CDI data) in 23 states and the District of Columbia participated in the intervention. There was a statistically significant decrease in CDI incidence over the study period, from 7.0 cases per 10 000 patient-days in the preintervention period to 5.7 cases per 10 000 patient-days in the postintervention period. However, this decrease appeared to be part of a temporal trend rather than due to the study intervention. Limitations: Commitment to and adherence with recommended infection prevention practices before and after the intervention were not assessed. The intervention period was relatively brief, and patient-level data were not available. Conclusion: Although a statistically significant decline in hospitalonset CDI was observed, this trend appears to be unrelated to the study intervention.