Purpose: The market of bottled water is one of the largest in the world. Paradoxically, the consumption of water in plastic bottles is highest in countries rich in the potable tap water of excellent quality. This paper aims to gain a better understanding of the factors that foster or hinder the intention to use refillable water bottles by university students and to determine whether their study program played a moderating role. Design/methodology/approach: Within the framework of Ajzen's theory of planned behavior (TPB), this paper conducted this cross-sectional study to understand the influence of attitudes, norms and perceived behavioral control (PBC) on the intention to drink tap water from reusable bottles. Italian university students (n = 540) majoring in the hard (42.4%) or the soft (57.6%) sciences completed an anonymous self-report questionnaire. Findings: For both groups, there was a significant association between attitudes and intention to use a refillable water bottle. The intention to drink tap water was also influenced by PBC among the hard science students, whereas among the soft science students the descriptive norm exerted a significant influence. Originality/value: This is the first application of TPB, a well-established theoretical and methodological framework, to understand the intention of university students to drink tap water from reusable bottles. Within the framework of TPB, this study is the first to address this specific pro-environmental behavior and explore the potential moderating role of university studies programs, which proved significant.