Archaeological starch grains consistent with those produced and stored in modern cojoba (Anadenanthera peregrina) seeds were identified, for the first time in the West Indies, in a coral milling base recovered in a small precolonial habitation site of Eastern Puerto Rico, in a context dated to A.D. 115–1250. Ethnohistoric, ethnographic, and previous archaeological data on cojoba from the West Indies and South America were surveyed in order to form plausible sociocultural interpretations of the findings.