It has a single thick, leathery leaf and up to twenty five strongly scented, lemon yellow flowers with brown blotches.

The flowers are strongly scented, insect pollinated and open freely on warm days.

[2][3][4] Thelymitra sargentii was first formally described in 1930 by Richard Sanders Rogers from a specimen collected by Oswald Sargent and the description was published in Transactions of the Royal Society of South Australia.

[6][7] The freckled sun orchid mainly grows near shrubs and small trees where it benefits from runoff during rain.

[2][3][4][8] Thelymitra sargentii is classified as "not threatened" by the Western Australian Government Department of Parks and Wildlife.