Increases in overall marine primary productivity and export production in high-nutrient, low-chlorophyll regions of the ocean have, particularly during dry and dusty glacial periods, been hypothesized to be linked to the enhanced delivery of iron. In the modern ocean, iron availability limits production in high-nutrient, low-chlorophyll regions, and may be important in lower-nutrient settings as well. Here, we assess the relationship between productivity and iron in sedimentary records from the high-nutrient, low-chlorophyll region of the equatorial Pacific Ocean over the past million years. We find strong links between iron input, the export and burial of biogenic silica (opal) and total export production. Our data demonstrate that iron accumulation was more closely tied to the accumulation of opal than any other biogenic component, with high iron input associated with substantially increased opal sedimentation. The strong links between iron and opal accumulation over the past one million years are in agreement with the modern biogeochemical behaviour of iron and silica, and the response of the diatom community to their mutual availablity. Our data support earlier suggestions of a biological response to iron delivery over geologic timescales.