Emergency Departments (ED) are critical access points for individuals at increased risk for acquiring HIV infection. Expanding ED-based HIV screening programs to provide HIV prevention services (HPS), including pre-exposure prophylaxis (PrEP), may fill an important public health gap.This was a mixed-methods, type 3 hybrid implementation effectiveness study of seven California EDs that integrated HPS for HIV negative patients between September 2021 and March 2023. A data collection instrument was used to obtain care cascade metrics. Semi-structured interviews were performed to understand the procedures for determining HPS eligibility and for making HPS referrals. Conclusion: ED HIV screening programs can be leveraged to implement HPS. Different models for identifying and referring eligible patients to HPS allow for flexible integration. Each model has strengths and weaknesses for addressing the prevention care cascade and for informing practice.