Tetranychidae is one of the most extensively studied groups of phytophagous mites due to its substantial economic importance. Commonly known as spider mites, these species produce fine multifunctional silk web on plant surfaces. Infestations often remain undetected until visible plant damage occurs as populations increase. Despite their global distribution and importance, species-level identification, particularly within the genus Tetranychus, remains challenging due to their size and strong morphological similarity among species. Although more than 1,360 species are currently recognized worldwide, only 19 species representing eight genera have been recorded in Canada. These include single species of Aponychus, Lindquistiela, and Pseudobryobia; two species each of Oligonychus and Panonychus; three of Eotetranychus; four of Bryobia; and five of Tetranychus. Despite their economic relevance, spider mite diversity in Canada remains poorly documented. Here, we report a newly identified species of Tetranychus damaging greenhouse-grown tomato crops in southwestern Ontario, Canada. Mite specimens were collected from tomato leaves in a commercial greenhouse in Leamington, Ontario, Canada, in summer 2023. An integrative taxonomic approach combining morphological examination of males and females with analyses of ITS and COI sequences enabled the accurate delimitation of this new species. Specimens were mounted in Hoyer’s medium and examined under an Olympus BHS compound microscope equipped with phase contrast, illustrations were prepared with a Wacom Intuos Pro L pen tablet using stacks of photographs acquired from a AmScope® MU1803 camera and imported to Adobe Illustrator® CS5. Setal nomenclature follows Lindquist (1985). The holotype and part of the paratypes series are deposited in the Institute of Pesticides and Environmental Protection, Belgrade, Serbia, the remaining paratypes are housed at Acari reference collection at UMR Center de Biologie pour la Gestion des populations, Montferrier-sur-Lez, France and at the Department of Biology, The University of Western Ontario, Canada. Morphological examination revealed that this species is a Tetranychus(Tetranychus) whose male aedeagus bears a very large knob with a well-developed, rounded anterior projection, a reduced acute hawk-beak posterior projection, and a rounded dorsal margin bearing a distinct indentation located between the anterior and posterior projections. Morphometric data, together with molecular analyses, confirm that these specimens represent a previously undescribed species, herein designated (Tetranychus) n.sp. This first report highlights an emerging pest causing damage in tomato cultivation and underscores the likelihood that additional undescribed tetranychid species remain to be discovered in Canada.