A great deal of research has been carried out to increase the availability of naturally-occurring proteins, or obtained from secondary products derived through industrial processes. As a result of the industrial exploitation of the native hazelnut (Gevuina avellana) in Chile, a defatted residue is obtained which eventually could be utilized as a human food. To determine the complementary potential capacity of the defatted hazelnut flour and pea flour, a study was carried out in weaning rats of the Wistar strain, as follows. The biological evaluation considered diet formulation with defatted hazelnut flour and pea flour in the 30:70, 50:50, 60:40 and 70:30 proportions, respectively. The NPR values obtained in this evaluation of the assay diets were: 3.4, 3.5, 3.9, 4.1 and 4.1, in comparison with 3.7 for casein. In percentage terms, the 4.1 NPR value was 11% higher than that obtained for casein. The maximum protein quality was observed when the two protein sources were mixed in the 60:40 and 70:30 (w/w) ratios. In regard to true digestibility, there were no significant differences among the experimental diets, but were lower than casein. The results of this study demonstrate that the defatted hazelnut flour constitutes an attractive nutritional alternative for the amino acid supplementation of cereal and legumes, the latter being of habitual consumption by the Chilean population.