Minority women in the United States are at a higher risk of iron deficiency and less likely to report use of prenatal supplements compared with non-Hispanic white women. Little information exists on the perceived benefits and barriers to prenatal supplement use. We analyzed the results of 12 focus groups conducted with African-American and Hispanic women (n=104). Groups were equally divided into consistent (five to seven times per week for 3 or more months) and inconsistent (zero to four times per week for 0 to 2 months) users and by race/ethnicity. We examined motivators and barriers to prenatal supplement use and identified common themes; we also compared responses between consistent and inconsistent users, and between African American and Hispanic women. For all groups, positive effects, convenient supply, affordability, and reinforcement by health care providers enhanced adherence. Common barriers were prenatal supplement qualities, adverse effects, and poor communication from health care providers about the benefits of use. Common motivators among consistent users included social network reinforcement of daily intake and fear of adverse effects to the fetus if prenatal supplements were not taken. Common barriers among inconsistent users included skepticism toward the efficacy and necessity of prenatal supplements and the health care provider assenting to nonadherence. Prenatal supplement use was influenced by multiple factors in women's daily lives. Adherence will likely be enhanced by reducing barriers related to prenatal supplement qualities and adverse effects, improving social network support, and improving health care provider interactions.