PurposeDrawing on the three flow-channel model and the stimulus–organism–response model, this research aims to understand how the influence of interactivity on purchase intention is mediated by the state of flow.Design/methodology/approachThis research entails a neurophysiological experiment combined with a survey-based study. This study analyzes, first, participants' heart rate variability through the parasympathetic and sympathetic indexes during five different activities, and, second, the mediating effect of flow through a structural equation model.FindingsThis study contributes to research on the role of flow in interactive marketing. The findings reveal that flow state is associated with less stressful activities, such as navigating highly interactive websites and playing online games. This research confirms the mediating effect of flow between interactivity and purchase intention.Originality/valueThis paper contributes to interactive marketing and flow theory by combining traditional methods with a peripheral physiological technique that draws on neuroscience. In addition, it confirms the positive but indirect effect of interactivity on purchase intention in online contexts.