The University of North Carolina (UNC) is a project office of the University of North Carolina at Chapel Hill to conduct HIV prevention research in Vietnam. We have been conducting a number of randomized control trials (RCTs both behavioral and clinical research in men and women from general and key populations in Vietnam for 15 years. In collaboration with the Vietnam Administration of HIV/AIDS Control (VAAC) and Hanoi Medical University, The UNC is conducting a pragmatic implementation trial comparing two Intervention Mapping implementation approaches for scale-up of the evidence-based intervention (EBI), referred to as System Navigation and Psychological counseling (SNaP), at 42 HIV testing sites, in 10 provinces of Vietnam, considering effectiveness, cost, and the characteristics of HIV testing sites achieving successful or unsuccessful implementation. This study is a cluster randomized, controlled implementation trial. The two Intervention Mapping implementation approaches are the one size fits all Intervention Mapping arm (IM) and the tailored Intervention Mapping arm (TIM). The intervention used in the study combines systems navigation and psychosocial counseling for people who inject drugs (PWID), and it is designed to facilitate PWID’s engagement in HIV and substance use care.