Background: Almost all babies are breastfed in Papua New Guinea (PNG); yet appropriate breastfeeding practices are not always followed. Aim: To explore the perspectives of first-time mothers in rural PNG on how the language and discourse of grandmothers about infant feeding influence their breastfeeding practices. Methods: A critical discourse analysis (CDA) approach was used to theoretically frame the analysis of twenty first-time mothers’ narratives. Findings: Analysis revealed three themes: (i) prescribed knowledge repository, (ii) social control and dominance, and (iii) disapproval and role conflict, which provides an understanding of grandmothers’ differing views and positions on infant feeding practices and their influence on breastfeeding. Conclusion: This study shows that grandmothers remain influential in infant feeding practices in rural PNG. There appears to be a societal expectation that empowers grandmothers in the maternal decision-making processes regarding breastfeeding practice. Grandmothers’ influence includes the early introduction of complementary foods to infants less than six months old. Interventions aimed at promoting, protecting, and supporting breastfeeding need to include grandmothers.