Thomasia tenuivestita is a species of flowering plant in the family Malvaceae and is endemic to the south-west of Western Australia.

It is a shrub with its new growth covered with greyish, star-shaped hairs, and has egg-shaped leaves, and racemes of mauve flowers.

The flowers are up to 12 mm (0.47 in) in diameter, the sepals mauve and hairy, the petals small and rounded.

[6] This thomasia grows in woodland and heath, often between granite boulders or in swampy places, in scattered populations near Coorow, Badgingarra, Wongan Hills, Hyden and York in the Avon Wheatbelt, Geraldton Sandplains, Jarrah Forest and Mallee bioregions of south-western Western Australia.

[2][3] Thomasia tenuivestita is listed as "Priority Three" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions,[3] meaning that it is poorly known and known from only a few locations but is not under imminent threat.