Groundwater management depends on the effective collaboration between water agencies and users. Beyond agreeing on sustainable levels of extraction, a key challenge is that extraction rules are followed. Yet experience has shown that compliance cannot be taken for granted. Enforcement—monitoring compliance and punishing infractions—has been essential to foster cooperation and reduce illegal extractions; yet it is a costly undertaking that often erodes trust between users and authorities. These issues are exacerbated in large groundwater basins due to the sheer number of users and limited resources available for regulatory action. In this context, new methods to study rule-adherence and rule-breaking behaviour are of great interest and value to groundwater management practice globally. The “Groundwater Commons Game” (GCG) is a novel approach to explicitly address these issues and help managers to better understand how rule-breaking behaviour can be discouraged. To this end, we use agent-based simulation to synthesise well-known principles of human cooperation and collective action, and to couple physically-based groundwater models with models of human behaviour grounded on the World Values Survey. The GCG, for the first time, reveals how culture drives groundwater conservation at the global scale. We focused on quantifying the likelihood of compliance emerging under regulated and nonregulated conditions, and how cultural values affect the speed at which compliance norms spread and their stability. Our results suggest that non-enforcement measures, such as leadership programs that engage a small fraction of compliance champions, could trigger more rapid responses to groundwater depletion (and its associated impacts) compared to enforcement. Similarly, we quantified the deleterious effects that a minority of rule-breakers can have on groundwater conservation. Overall, our work highlights the need to incorporate agent-based modelling into the groundwater toolkit as a way to progress towards systematic modelling of coupled human and groundwater systems.