The cork oak (Quercus suber) is a key tree species in Portugal, with significant socioeconomic and ecological importance. One of the main threats to cork quality is the beetle Coraebus undatus, whose larvae burrow internal galleries in the trunk, compromising the commercial value of the resource. Although the impact of this pest has been documented in southern Portugal and Spain, its occurrence in the Northeast region remained unconfirmed. The objectives of this study were to assess the presence and distribution of C. undatus in northeastern Portugal and to identify the environmental and structural factors influencing infestation. A survey of 680 cork oaks was conducted between March and June 2024, recording the presence of galleries, trunk characteristics, surrounding vegetation, and geographic coordinates. The results revealed that 59% of the trees had visible galleries, with an average of 4.52 ± 0.18 galleries per tree. Most were located between 50 and 150 cm above the ground, with no significant preference for a particular cardinal direction. Trunk diameter and latitude showed a positive association with the presence of the insect, while plots without ground vegetation exhibited a lower probability of infestation. This study represents the first confirmed record of C. undatus in northeastern Portugal, revealing higher levels of infestation than those reported in other regions. These results highlight the urgent need for monitoring and phytosanitary management to ensure the sustainability of the cork oak forest.