This study examines organizational, provider, client, and test-event level predictors of HIV partner notification (PN) discussion and agreements based on providers’ most recent HIV-positive post-test counseling session. Staff (n = 621) were sampled from for-profit, nonprofit, and county government HIV testing organizations (N = 159) in Los Angeles County from 2003 to 2007. Among providers who conducted an HIV-positive post-test counseling session (n = 204), 65% discussed PN but only 10% had confirmed agreement to provider-involved PN (PIPN). In multi-level regression analyses PN discussion was predicted by provider HIV-test training and knowledge, and patients requesting a test while presenting HIV/AIDS symptoms. The strongest predictor of PIPN agreement was public health HIV testing settings followed by counseling by program managers or infectious disease specialists across settings. None of the injecting drug users or patients presenting with AIDS, but not requesting a test, agreed to PIPN. Organizational and provider-level interventions on PN will be needed to realize cost-effective benefits of expanded HIV testing and counseling.