IntroductionBreastmilk is considered the gold standard for infant nutrition. Breast feeding is recommended as the sole source of nutrition between birth until around 6 months of age and should be continued beyond this age as complementary foods are introduced. While breast feeding initiation is generally high in developed countries, continuation of breast feeding appears to drop rapidly. This is a prospective observational study of life that aims to characterise a current picture of infant feeding practices across the first year, and motivations for feeding practices, and to identify barriers and enablers for breast feeding.Methods and analysisCaregivers with newborn singleton infants of normal birth weight are approached on the postnatal units of three hospitals in South Australia, or through targeted online advertising campaigns promoting the study. Caregivers are asked to complete surveys when their infant reaches 3, 5 and 7 weeks’, and at 3, 4, 5, 6, 9 and 12 months of age. Initially, baseline characteristics, intentions and preferences for infant milk feeds, as well as reasons for preferences are captured. Latter surveys query how infants are being fed, difficulties or barriers to breast feeding, as well as any enablers (if breast feeding). Once infants reach 5 months of age, surveys capture complementary feeding. A large opportunistic sample from the Adelaide community with a minimum of 1000 mother–infant pairs will be enrolled. The data will be analysed descriptively and using regression models.Ethics and disseminationWomen’s and Children’s Health Network Human Research Ethics Committee reviewed and approved the study (approval no HREC/19/WCHN/140, approval date: 22 November 2019). Study results will be disseminated through academic meetings, peer-reviewed journals, in-services for postnatal healthcare services, results letters for participants and social media.Trial registration numberACTRN12620000529943.