OBJECTIVE: To identify enabler and barrier mechanisms that impact project implementation, from a review of 127 completed projects intended to reduce harms associated with problematic alcohol and licit drug use in Australia. DESIGN: Data comprised archival material (proposals, reports). A coding framework was developed from the literature and a sample of projects; two researchers developed and refined the framework. Open coding was used to identify factors impacting implementation, followed by pattern coding to identify underlying mechanisms. SAMPLE: Project categories were developed from funding orientation and main activities projects were: enhancing organizational systems and processes (39), training and workforce development (18), community education and prevention (37) and client engagement and treatment (33). Thirty-five projects (28%) were in non-capital city locations. RESULTS: Nine enabler and ten barrier mechanisms were identified, for example, 'project planning and design' and 'wider service system challenges'. Three enabler mechanisms were more likely to be identified for non-capital city projects; 'external communication and relationships' (83% vs 70%), 'sensitivity to service users and settings' (49% vs 40%) and 'funding and resourcing' (40% vs 35%). Most barrier mechanisms were identified for a higher proportion of non-capital city projects, particularly 'identifying and retaining personnel' (54% vs 34%), 'engaging communities and partners' (46% vs 26%) and 'organizational governance and capacity' (29% vs 5%). CONCLUSIONS: Project implementation in non-capital city locations requires particular attention to project planning and design, staffing and organizational well-being. Policy initiatives and planning proposals might consider enabler mechanisms along with strategies to minimize barrier mechanisms to support successful implementation.