The arching fronds of Rumohra adiantiformis grow lace-like and somewhat triangular to ovate in shape on sturdy stalks. Their structure is pinnate, three or four times divided, the pinnae alternating and ascending on the rachises. The primary and secondary pinnae are stalked, the ultimate segments oblong, rounded or obtusely angled.

The dark green, yellow green to dull green pinnae are glossy, sometimes faintly so and leathery. The lower frond surface is paler and duller, somewhat scaly and dotted along the margins with brown or black sori (Bean and Johns, 2005; iNaturalist; www.nzpcn.org.nz).