(1) Background: Policies and laws in several jurisdictions across the globe have aimed to promote harm minimisation or reduction, through the implementation of Needle and Syringe Programs (NSP) for People who inject drugs (PWID), for whom abstinence may not be possible or desired. While NSPs hold great promise, their implementation qualities are understudied. (2) Aim: We aimed to examine the implementation quality priorities of NSP providers and PWID consumers in an Australian setting. (3) Method: This study utilised a Quantitative-qualitative (QUAN-qual) mixed methods approach. Survey participants included both PWID ( = 70) and NSP providers ( = 26) in Australia. (4) Results: Results following non-parametric data analysis indicate NSP providers prioritised NSP implementation qualities in the following order: compatibility, observability, relative advantage, resourcing and trialability. Contrary to which, PWID prioritised resourcing, compatibility, relative advantage and trialability, respectively. Findings demonstrate that efficacy of implementation qualities is dependent on the juxtaposition of service provision and utilisation whereby implementation quality priorities are balanced. (5) Conclusions: This research presents novel findings guiding NSP harm reduction programmes for sustainability framed on provider and consumer implementation quality priorities. We envisage future studies on boundary conditions of NSP harm reduction implementation in other jurisdictions.
