While the conceptually related fields of sustainability and psychological well-being have been informed by extensive research in recent years, efforts to integrate these fields are yet to be systematically advanced. This lack of integration has left the nexus between sustainability and well-being largely underexplored and conceptually underdeveloped. Tourism offers a novel context within which to explore the intersection. Consequently, this paper critically assesses the relationship between sustainability-related decisions and tourist well-being. It is informed by the analysis of thirty semi-structured in-depth interviews that critically explored the holiday experiences of tourists while travelling internationally. Analysis revealed that both responsible and irresponsible tourist behaviours are interconnected with tourists’ psychological well-being and are influenced by external barriers and internal conflicts. Responsible behaviours were found to contribute to eudaimonic well-being through a heightened sense of perceived integrity. Conversely, irresponsible behaviours trigger negative self-appraisals, enacting coping mechanisms and generating guilt. This manuscript presents the triple helix model detailing the complex and interconnected relationship between (ir)responsible behaviour and psychological well-being in tourism experiences. Future research should consider the intricate connections between tourists’ sustainability-related decisions and psychological well-being as central to the developing sustainable tourism research agendas.