Background: Formula brands have modified the ingredients in standard infant formulas and extensively market modified formulas, claiming benefits for infants that are not supported by scientific evidence. This exploratory study examined the proportion of infant caregivers who reported serving modified formula, demographic differences, and reasons for providing them. Methods: This is a cross-sectional online survey of US caregivers of infants (6-11 months) who provided formula in the past month (N = 436). Participants reported the type of formula served most often and agreement with potential reasons for provision. Logistic regression assessed the odds of serving modified formula by demographic characteristics. MANOVA examined differences in agreement with purchase reasons between caregivers by the type of formula provided. Results: Approximately one-half (47%) of participants reported serving modified formula most often; sensitive and organic/non-GMO were the most common types provided. Caregivers in the middle-income group were most likely to serve modified formulas, but the provision did not differ by other demographic characteristics. Agreement with reasons for providing was highest for "pediatricians recommend" and "benefits my child" (M = 4.2 out of 5). Agreement with "my pediatrician prescribed" and "natural ingredients" was significantly higher for modified vs. standard formula providers. Conclusion: Widespread provision of modified formula by infant caregivers raises concerns due to its higher cost and the lack of scientific evidence supporting benefits for babies. These findings suggest that regulations limiting unsubstantiated formula claims and restrictions on misleading marketing to consumers are necessary. Additional research is needed to understand pediatricians' perceptions of modified formulas and reasons for recommending them to patients.