The wood anatomy of Quercus faginea, an oak native to the Iberian Peninsula and the Maghreb in Africa, is described and age trends of fibres and ray dimensions are recorded. The analysis was made on a total of 20 trees from two different sites in Portugal. The wood structure within both sites was similar. Quercus faginea shares its microscopic characteristics with other species of the white oak group; i.e., it was not easily distinguishable from other European oaks. The wood is ring porous with wide multiseriate rays and a high proportion of fibres and vasicentric tracheids. There was an increase of fibre and ray dimensions from the pith outwards. Fibre length started to stabilize around 30 years of age up to 50–60 years and decreased afterwards under a traditional rotation period (100–150 years). Linear and polynomial adjustments fitted better the fibre variation at younger and older ages, respectively. Rays were quite homogeneous within the trees. Cambial age accounted less to total variation than individual trees at both sites; i.e., tree-to-tree variation is greater than variation related to maturation or cambial age. The average dimensions of fibres and rays were similar between sites.