As African countries undergo rapid digital transformation, sustainability campaigns increasingly rely on mobile and social media platforms to reach diverse populations. However, the effectiveness of these digital interventions depends not only on technological access but on the pragmatic and cultural appropriateness of the messages conveyed. This chapter examines how sustainability messaging operates across multilingual African contexts, specifically in Nigeria, Kenya, and Ghana, drawing on theories from pragmatics, intercultural communication, and cultural linguistics. Through a grounded analysis of digital messages delivered via WhatsApp, Facebook, SMS, and mobile applications, the chapter explores how speech acts, politeness strategies, metaphor use, and narrative framing affect public interpretation and engagement. The study identifies key areas where pragmatic failures, such as overly direct speech or culturally inappropriate metaphors, have led to misinterpretation or resistance. Conversely, it highlights the communicative power of culturally anchored strategies, including the use of proverbs, storytelling, and identity-based appeals. Audience responses are analyzed to understand how digital messages are interpreted cognitively, emotionally, and behaviorally within local semiotic frameworks. The chapter argues that effective sustainability communication in Africa must transcend mere translation to engage local communicative norms, ethical codes, and symbolic repertoires. It calls for the integration of linguists, cultural mediators, and community leaders into message design and advocates for participatory, inclusive models that reflect local epistemologies. By advancing a linguistically and culturally responsive framework, the study contributes new insights into the human dimensions of digital sustainability in Africa.