Childhood anemia remains a significant driver of morbidity in low- and middle-income countries, including Peru. To identify behavioral challenges to using micronutrient powder (MNP) that is given to supplement children's diets and prevent anemia, we applied a behavioral design approach to interviews and focus groups with 129 caregivers in Arequipa, Peru. We examined 3 key points in the decision-making process: accessing MNP through the health system; forming intentions to use MNP; and MNP use at the time of child feeding. Using the NUDGE (Narrow, Understand, Discover, Generate, Evaluate) approach, we identified the following behavioral barriers and facilitators: (1) caregivers' experiences with health care providers shaped their motivation to access MNP; (2) caregivers felt accessing MNP at clinics was inconvenient and created hassle factors; (3) caregivers' mental models about anemia prevention shaped MNP intentions and use; (4) caregivers' salient negative experiences could have caused them to stop giving MNP; (5) caregivers forgot to give MNP if they did not have cues to remind them but could be prompted with salient cues; and (6) caregivers were affected by emotional, cognitive, and attentional factors during feeding that were difficult to anticipate. Our results, based on a behavioral design approach, suggest opportunities to adapt current messaging, counseling, and education around MNP use. Adaptations include providing culturally relevant messages, leveraging caregivers' emotional and cognitive states, and encouraging small but impactful changes to feeding routines to address barriers to MNP use.