This study investigates how social media exposure shapes young adults’ attitudes and intentions toward sustainable products in Kuwait—a high-income, oil-dependent context undergoing a digital and cultural shift. Integrating the Theory of Planned Behavior (TPB) and the Elaboration Likelihood Model (ELM), the research explores the mediating roles of environmental responsibility, social influence, and consumer attitudes in the formation of sustainable purchase intentions. Data were collected via an online survey of 702 respondents aged 18–30 and analyzed using structural equation modeling (SEM). The findings reveal that social media usage significantly influences sustainable purchase intention, social influence, and consumer attitudes. Environmental responsibility emerges as a key driver of both attitudinal and normative pathways. Notably, the study finds no direct link between consumer attitude and intention, highlighting a persistent attitude–behavior gap. The results offer theoretical insights into digital persuasion and normative influence while providing practical guidance for marketers and policymakers promoting sustainability in digitally connected, non-Western societies.