The aim of this work was to study mite diversity in vineyard plots planted with Cabernet Sauvignon and Pinot Noir cultivars and on associated non-cultivated plants in two viticultural regions of Rio Grande do Sul State, Brazil. Monthly assessments of leaves and buds of vines and of non-cultivated plants were undertaken between October 2006 and September 2007. Twelve thousand mites belonging to 17 families and 46 genera and representing 61 mite species were collected. The most abundant phytophagous mites were Calepitrimerus vitis, Colomerus vitis and Panonychus ulmi on grapevines. Among the predatory mites, the most abundant were Neoseiulus californicus and Agistemus floridanus. The non-cultivated plants species that showed the greatest richness of mites were Plantago tomentosa, Plantago lanceolata and Senecio sp. The most abundant phytophagous mites on non-cultivated plants were Tetranychus ludeni and Brevipalpus phoenicis in the viticultural regions of Bento Gonçalves and Candiota, respectively, and Pronematus anconai was generally the most abundant predatory mite. In the region of Bento Gonçalves, species richness and abundance in the agroecosystem were far higher than in the region of Candiota.