A cross-sectional analysis was conducted using data from the Millennium Cohort Study. Logistic regression was carried out on a sample of 17,308 respondents, adjusting for individual- and familial-level socio-demographic characteristics. Neighbourhood deprivation was independently and inversely associated with breastfeeding initiation. Compared with the least deprived areas, the likelihood of initiating breastfeeding was 40% lower in the most deprived neighbourhoods (OR: 0.60, 95% CI [0.50, 0.72]). The relationship between both exclusive and any type of breastfeeding at 3 and 6 months respectively with neighbourhood deprivation after adjustment for potential confounders was not entirely linear. Breastfeeding initiation (OR: 0.78, 95% CI [0.71, 0.85]), exclusivity for 3 months (OR: 0.84, 95% CI [0.75, 0.95]), and any breastfeeding for 6 months (OR: 0.82, 95% CI [0.73, 0.93]) were each reduced by about 20% among mothers who perceived their neighbourhoods lacking safe play areas for children. Policies to improve breastfeeding rates should consider area-based approaches and the broader determinants of social inequalities.