Background: There is no clinical definition of iron deficiency (ID) in infants <12 months, despite the increased risk in infancy. Low iron status may be associated with negative brain and cognitive performance outcomes that persist after iron repletion, but results are mixed. Research is needed to combine measures of iron status, brain function, and cognitive performance in early infancy. Objectives: To determine whether, in infants aged 4-6 months: 1) there is an association between low iron status and brain responses to a memory task; 2) low iron status is associated with memory performance; and 3) brain function mediates the hypothesized relationship between iron status and memory performance. Methods: We measured iron status, brain function with event-related potentials (ERP) during a memory task, and memory performance in 4-6 month old infants. Results: Serum ferritin (sFt), but not hemoglobin was associated with an attenuated ERP response to novel versus familiar stimuli. Estimated body iron and sFt were associated with novelty preference by trial (%Novtrl ) after removing inattentive trials, and the association between sFt and %Novtrl was stronger in infants with low iron stores (sFt <45.0 [MICRO SIGN]g/L). The data did not support our hypothesis that brain function mediates the relationship between iron status and memory performance. Conclusions: ERP measures of brain function and a memory performance task are sensitive to iron status in early infancy, but more research is needed to link iron status to memory via brain function.