<p>University students are often preoccupied with classes, examinations, and projects, leaving little attention to their gut health and probiotic consumption. This neglect can lead to problems such as mental fatigue, weakened immunity, and reduced concentration. Probiotics, however, represent a small but effective investment that can enhance quality of life and academic performance—yet many students overlook this opportunity. This study was conducted to identify the factors influencing Iranian students’ use of probiotic products. The statistical population comprised undergraduate, graduate, and doctoral students at the University of Agricultural Sciences and Natural Resources in Khuzestan Province. The research employed an expanded Theory of Planned Behavior (TPB), incorporating risk perception (RP) and social media (SM) variables into the traditional framework. Data were collected through a questionnaire survey and analyzed using structural equation modeling (SEM). Findings revealed that the original TPB explained 52.1% of the variance in students’ behavioral tendencies toward probiotic consumption. The three core constructs—attitude, perceived behavioral control (PBC), and subjective norms (SN)—all exerted positive effects. Importantly, the expanded TPB, with the addition of RP and SM, increased explanatory power by 23.7%. Among the extended variables, SM influence emerged as the most significant factor, suggesting that policymakers and health promoters should prioritize media-based strategies to encourage probiotic use within student populations.</p>