<p>In the era of digital transformation, Corporate Social Responsibility (CSR) practices have become a core component of branding strategies aimed at strengthening long-term consumer relationships. This study examines how the interpretation and credibility of CSR messages on social media influence consumer engagement, offering a communication-centered perspective on the dynamics between message signals, audience perception, and behavioral response. Data were collected through an online survey of 350 Vietnamese consumers who regularly purchase dairy products. Drawing on signaling theory, the research examines how audiences interpret CSR messages from brands and how these interpretations influence their online behavioral responses.The findings indicate that CSR credibility serves as a significant and positive mediator, transforming CSR-related perceptions into active consumer participation. Conversely, brand image and satisfaction function as signal noise that reduces the clarity and persuasiveness of CSR communication in motivating consumer actions. The results highlight the importance of transparent and consistent CSR communication to enhance brand credibility in the digital environment. The study contributes to both theoretical and managerial perspectives by offering insights into how dairy companies in Vietnam can refine their online CSR strategies to cultivate stronger consumer attachment and sustained brand advocacy.The originality of this paper lies in its integration of signaling theory with CSR communication to explain consumer engagement in an emerging market context, its novel conceptualization of observable signals and signal noise, and its empirical validation of CSR credibility as a key determinant of digital consumer behavior.</p>