This study investigates how digital campaigns on social e-commerce platforms foster environmental awareness and shape sustainable behavior among Vietnamese university students. Guided by the Stimulus–Organism–Response (S–O–R) framework, the research examines the effects of social e-commerce exposure and eco-themed content on students’ environmental sensitivity and behavioral responses. A structured questionnaire was designed using Google Forms and distributed via online forums and direct invitations to university students, resulting in 207 valid responses collected through purposive sampling. Measurement reliability was confirmed (Cronbach’s Alpha = 0.861–0.898), and the structural model demonstrated good fit (CFI = 0.989; RMSEA = 0.024). Structural Equation Modeling (SEM) results revealed that both social e-commerce exposure (β = 0.308) and eco-themed content (β = 0.371) significantly enhanced environmental awareness, which in turn predicted sustainable behavior (β = 0.436). Group comparison further highlighted significant differences by gender (p = 0.047), study year (F = 594.196), and prior green product experience (F = 428.127). These findings underscore the critical role of emotionally driven, environmentally focused digital content in positively influencing youth behavior. The study provides empirical evidence from Vietnam, enriching the literature on social e-commerce, digital marketing, and sustainable consumer behavior.