Elliptic-oblong or obovate to orbicular leaves are scattered and alternate along the simple, glabrous stem.

Stylidium darwinii is only known from Anshi National Park in the Uttara Kannada district of Karnataka, India.

Its habitat is recorded as being moist gravelly soils on the outskirts of evergreen forests near roadsides at an altitude of 530 m (1,739 ft).

[1] This species was first located in 2007 as part of a floristic survey of Anshi National Park and was first formally described by Sachin A. Punekar and P. Lakshminarasimhan in 2010.

They did, however, note that S. darwinii is closely allied with S. kunthii, S. inconspicuum, and S. tenellum.