The Azores archipelago (Macaronesia), composed of nine volcanic islands, is a historical crossroads for vessels from the Americas and Europe, with biodiversity threatened by invasive plant species. While terrestrial biodiversity has been studied, groups like spider mites (Tetranychidae) remain poorly known, with only six species previously reported from limited sites. This study surveyed spider mite diversity across the archipelago through taxonomic identification and assessed host plant associations. We provide first records for the Azores, evidence of new species, and expand known geographic distributions and host ranges. Field collections were carried out in 10/2015 and between 04/2024 and 09/2025 across six islands (São Miguel, Pico, Flores, Faial, Graciosa and Santa Maria). Sampling yielded 406 samples from approximately 70 localities, covering 66 host taxa from 37 plant families, including native and exotic species. Mites were identified using an integrative taxonomy approach combining morphological examination and COI DNA barcoding. Twelve tetranychid species across six genera were identified, with Oligonychus yothersi and Tetranychus ludeni emerging as the most widespread host-generalists. Six new records were established (Eotetranychus rubiphilus, Eotetranychus sexmaculatus, Tetranychus evansi, Petrobia harti, Stigmaeopsis celarius and Stigmaeopsis nanjingensis), while the distribution of Panonychus citri, T. ludeni and Tetranychus urticae expanded within the archipelago. Novel host associations were reported for E. sexmaculatus (Polygonaceae) and T. ludeni (Magnoliaceae). Crucially, the occurrence of O. yothersi and T. urticae on endemic plants, alongside one Tetranychus (also recorded on exotic hosts) and two Oligonychus species currently under description, reveals a concerning niche expansion onto endemic flora. These results reinforce the Azores as an encounter point of introduced spider mite pests originating from The Americas and from Europe. This highlights the host range plasticity of invasive species, which can threaten sensitive insular ecosystems, and underscores the need for continued monitoring and biosecurity efforts to better understand and mitigate potential herbivore impacts on native Macaronesian flora.