Water crises constitute a challenge for humanity. Uncertain supply and growing demand are driving higher water theft, particularly by agricultural users who account for approximately 70% of global use. However, research into water theft is underexplored in all disciplines. This paper provides a conceptual framework and modelling approach designed to improve understanding of both individual and institutional barriers to water theft. The framework and model explore how effective detection, prosecution, conviction and penalties can be assessed. Three case studies test the validity of our framework. Our findings suggest that while individuals and companies may be responsible for the act of theft, the phenomenon reflects a systematic failure of arrangements (political, legal, institutional, and so on). In addition, when regulators fail to understand the value of water, inadequate prescribed penalties increase the risk of theft. We invite others to test our framework, apply our model and engage in a wider conversation about water theft. Water use may be a topic of increased research, but water theft remains understudied. This paper utilizes insights from three international case studies to inform on the systemic failures that sustain water theft.