Ischnocnema sanctaecrucis is a species of frog in the family Strabomantidae.

It has been found under rocks; males have been observed perching on small secondary vegetation.

Its range includes the Carrasco and Amboró National Parks.

The head is large and wider than long; the snout is short.

The dorsum is pale brown to dark brown with cream flecks; the skin is granular, with round keratinized granules and small, sparse, low, flat warts.