Green advertising messages often face challenges of abstraction and outcome ambiguity. To address this, we apply the framing effect theory to explore how concrete versus abstract expressions in green advertising interact with consumer perceptions. Drawing on the Stereotype Content Model (SCM), we propose a congruence framework: concrete messages align with competence appeals, while abstract messages align with warmth appeals. Through two experiments, we demonstrate that such congruence significantly enhances green purchase intention. Experiment 1 establishes the interaction effect between message framing (concrete vs. abstract) and appeal type (competence vs. warmth), revealing that concrete–competence and abstract–warmth pairings outperform mismatched conditions. Experiment 2 further validates advertising attitudes as a mediator and product involvement as a moderator, clarifying boundary conditions. These findings advance the theoretical understanding of framing effects in sustainability communication and offer actionable strategies for marketers: aligning message specificity (concrete/abstract) with appeal dimensions (competence/warmth) can amplify consumer engagement, particularly when tailored to product contexts.