This briefing summarises an ongoing research project examining conditions that contribute to effective working relationship between international development volunteers and local host-country counterparts. End-of-assignment surveys show that host-country managers (and volunteers) see the interpersonal elements of international development work as critical to the success of volunteer placements. Yet they also acknowledge that relationships between volunteers and host-country nationals are complex and challenging. To understand these cross-cultural relationships, a sample of Australian international volunteers and Vietnamese host-country counterparts were interviewed about their experiences collaborating on a range of international development projects between 2010 to 2015. The interviews canvassed the main outcomes of, and contributors to, effective and ineffective relationships. The study’s results suggest opportunities to improve the efficacy of international volunteer placements.