The use of groundwater resources for dry season irrigation has gained currency in Ghana. The north-east of the country has seen the cultivation of vegetables using groundwater from shallow aquifers; an emerging livelihood activity which lessens food insecurity and stems the tide of rural–urban migration. This practice in northern Ghana is deeply rooted in local knowledge. Using the Atankwidi catchment, this paper examines the role of local knowledge in understanding and exploiting groundwater for irrigation. A qualitative approach was used which allowed for in-depth catchment-level investigations, using group discussions, key informant interviews and informal discussions with irrigators, traditional leaders, earth priests, men, and women. Evidence from analysis revealed that local knowledge enabled farmers to locate groundwater points and determine the source and timing of groundwater recharge. Traditional communities are also able to identify the period for constructing wells. In addition, local knowledge enabled farmers to adopt strategies of conjunctively using groundwater with alternative water to cope with insufficient groundwater resources. We argue that local knowledge serves as a useful tool in sustaining dry season irrigation despite the challenges of a lack of government support and threats of global change.