The coronavirus disease 2019 (COVID-19) pandemic increased food insecurity among US households, however, little is known about how infants, who rely primarily on human milk and/or infant formula, were impacted. We conducted an online survey with US caregivers of infants under 2 years of age (N = 319) to assess how the COVID-19 pandemic impacted breastfeeding, formula-feeding and household ability to obtain infant-feeding supplies and lactation support (68% mothers; 66% White; 8% living in poverty). We found that 31% of families who used infant formula indicated that they experienced various challenges in obtaining infant formula, citing the following top three reasons: the formula was sold out (20%), they had to travel to multiple stores (21%) or formula was too expensive (8%). In response, 33% of families who used formula reported resorting to deleterious formula-feeding practices such as diluting formula with extra water (11%) or cereal (10%), preparing smaller bottles (8%) or saving leftover mixed bottles for later (11%). Of the families who fed infants human milk, 53% reported feeding changes directly as a result of the pandemic, for example, 46% increased their provisioning of human milk due to perceived benefits for the infant's immune system (37%), ability to work remotely/stay home (31%), concerns about money (9%) or formula shortages (8%). Fifteen percent of families who fed human milk reported that they did not receive the lactation support they needed and 4.8% stopped breastfeeding. To protect infant food and nutrition security, our results underscore the need for policies to support breastfeeding and ensure equitable and reliable access to infant formula.