A study on rapid routine HIV screening was mainly performed by nurses in 29 Emergency departments (EDs) in the Paris urban area. Individual and collective covariates of healthcare staff participation were analyzed, along with positioning regarding nurse autonomy for this activity. International studies confirm the interest of nurse screening. Twenty-five interviews with nurses, nurse supervisors, and physicians were performed in five departments. Staff participation is associated with motivation regarding HIV or prevention, a multidisciplinary approach, a generalist background, or brief professional experience, as well as the perception that the process is easy. Most nurses succeeded in offering and carrying out the test, and disclosing the negative results to patients. This activity was considered as an autonomy vector. After training sessions, HIV screening could become part of the nurse mandate of prevention in collaboration with physicians. This collaboration addresses a classic work division for nurse supervisors and doctors. However, a systematic implementation of HIV screening in EDs seems not to be feasible because of structural constraints. Autonomy for nurse-initiated HIV screening, extended to prevention and public health activities, is seen positively by nurses.