Children’s diets in their first 1000 days influence dietary preferences, eating habits, and long-term health. Yet the diets of most infants and toddlers in the United States do not conform to recommendations for optimal child nutrition. This narrative review examines whether marketing for infant formula and other commercial baby/toddler foods plays a role. The World Health Organization’s International Code of Marketing Breast-milk Substitutes strongly encourages countries and manufacturers to prohibit marketing practices that discourage initiation of, and continued, breastfeeding. However, in the United States, widespread infant formula marketing negatively impacts breastfeeding. Research has also identified questionable marketing of toddler milks (formula/milk-based drinks for children aged 12–36 mo). The United States has relied exclusively on industry self-regulation, but US federal agencies and state and local governments could regulate problematic marketing of infant formula and toddler milks. Health providers and public health organizations should also provide guidance. However, further research is needed to better understand how marketing influences what and how caregivers feed their young children and inform potential interventions and regulatory solutions.