BACKGROUND: Harm reduction has been identified as an important HIV prevention strategy for injecting drug users (IDUs) in Vietnam. However, to date only small geographically limited formal needle syringe programmes (NSPs) have been implemented; and little attention has been given to assessing the effectiveness of the piloted models. Using data from a qualitative evaluation of an NSP in northern Vietnam, this paper assesses the effectiveness of the intervention, examines barriers to the NSP, and documents lessons which can be applied to replicate and scale up interventions across Vietnam. METHODS: Data were gathered using key informant interviews, focus group discussions, in-depth interviews, observation and intercept interviews with IDUs and other project stakeholders. IDUs were introduced to the evaluation by peer educators (PEs). RESULTS: The project contributed to a shift toward safe injecting practices and safe disposal of used needles and syringes (N&S) among IDUs. Collection of used N&S positively influenced community attitudes toward PEs and IDUs. Reduced community discrimination, achieved as a result of project advocacy activities, encouraged IDU to access free needle syringes and other project services provided by PEs. Resistance from the local government officials and community members was turned into support for the programme through intensive advocacy activities. The project highlighted the importance of involving law enforcement in the programme and promoted a public health approach toward working with IDU. However, periodic police campaigns against drug use continued to be an obstacle to successful programme implementation and demonstrated the need for continued efforts to address the issue. CONCLUSION: Programme success is dependent upon community support. Resistance to NSPs can be overcome through a programme of intensive advocacy with community stakeholders including; local government, mass organizations, local residents, IDUs and their families. Garnering the support of law enforcement officials requires a sustained effort.