Teosinte (Dioon mejiae) is a dioecious tree native to Honduras, whose seeds are used to make flour for the preparation of traditional foods and beverages. The objective was to evaluate the nutritional and physicochemical composition of teosinte flour for the first time. Using diverse techniques, teosinte flour was found to be a high-calorie food rich in total carbohydrates and mainly composed of starch, with an amylopectin:amylose ratio of 2:1 and a concentration of resistant starch greater than 50%. Its proteins were similar to other cereals in which the essential amino acids glutamic acid, leucine, and especially lysine were the most important. Some 75% of its total dietary fiber was insoluble. The fatty acid profile was characterized by a high unsaturated fatty acid content in which oleic acid (C18:1) and linoleic acid (C18:2) predominated. As for minerals, teosinte flour had higher iron content, lower sodium concentration, and similar zinc, calcium, and phosphorus content to other cereal flours. We highlight that teosinte flour has nutrients and qualities that convert it into flour with excellent nutritional abilities and health benefits; it is also a very good industrial and technological alternative to be mixed mainly with types of flour from other sources.