Identifying alien species is important to ensure the early detection of biological invasions and survey shifts in species distributions in the context of global change. Here, we report on three alien bark and ambrosia beetles newly detected in Switzerland: Cyclorhipidion distinguendum (Eggers, 1930), C. pelliculosum (Eichhoff, 1878), and Hypothenemus eruditus (Westwood, 1834). These species were recorded for the first time during a comprehensive survey of saproxylic beetles accross major forest types and along an altitudinal gradient during the entire growing season in the southern Alps, in the canton of Ticino. Their local abundance and number of occurrences accross different lowland forest habitats, including alluvial forests of national importance, indicates that all three species are already naturalized. Given their polyphagy, it is likely that all three species will become more extensively distributed across Switzerland, with a yet unknown environmental impact.