Vietnam's uplands have been increasingly integrated into commodity production for global markets. This paper focuses on the role of the cassava trader in connecting upland villagers as cassava producers to an emerging global cassava market. In Vietnam's Central Highlands, ethnic minority villagers engaging in a mixed economy of subsistence and cash crop production still practice communal resource use and reciprocal labour arrangements – customs associated with the (contested) notion of ‘moral economy’. In this context, traders have strategically traversed the insider–outsider divide, enlisting trust and reciprocity to extend the patron–client relationship between traders and villagers. In the absence of state support for upland communities, these traders have embedded themselves within village social relations through the provision of multiple goods and services, including loans. Villagers turn to these traders during times of hardship through degrees of mutual dependence in often unequal trade relations. The ‘benevolence’ of the traders, however, is an explicit strategy to legitimise their economic benefits. The relationship is deepened because traders fill a vacuum in state services by providing technical support to farmers cultivating cassava. Beyond benefiting themselves, in their status as community ‘insiders’, traders promote market penetration into the uplands with associated social and environmental implications.