Sustainability-oriented advertising aligned with the United Nations Sustainable Development Goals (SDGs) significantly enhances Indian consumers’ purchase intentions through brand trust, moderated by corporate reputation and SDG literacy, as revealed by a six-month time-lagged survey of n = 421 respondents. Employing PLS-SEM, this study demonstrates that SDG-focused CSR advertising strengthens brand trust, which mediates 63% of the total effect on purchase intentions. Corporate reputation amplifies this relationship, with high-reputation firms achieving 23% greater purchase intention, while consumers in the top SDG literacy quartile exhibit 31% stronger trust-to-purchase pathways. The implications of the study highlight the need for the layered communication frameworks that navigate India’s evolving sustainability landscape.