Nothofagus alessandrii is an endangered species that is endemic to the Mediterranean area of Chile. There is no information on the anatomical structure of its seeds and there are few studies on the morphometric and germination differences between its populations. Therefore, the purpose of this study was to describe the morpho-anatomical structure of seeds of N. alessandrii in order to compare the morphology and germination four geographically distinct populations. This was done by selecting seeds of four different origins covering the entire latitudinal distribution of the species and measuring their size, shape, dry weight and germination in order to perform a comparative analysis. Results showed that the anatomical structure of N. alessandrii seeds is similar to that of other species of the Fagaceae family such as Fagus sylvatica. No differences were found between seeds from the four different origins in morphological characteristics or germinative power. Thus, it was not possible to demonstrate the existence of clinal variation, although the southernmost population showed differences in length and weight, suggesting that it may belong to a different ecotype.