It is an erect shrub, with linear leaves, and white or pink flowers with 40 to 55 stamens.

[2][3][4] Hypocalymma serrulatum was first formally described in 2003 by Arne Strid and Greg Keighery in the Nordic Journal of Botany from specimens Keighery collected 9 km (5.6 mi) east-north-east of Badgingarra in Badgingarra National Park in 1982.

[3][5] The specific epithet (serrulatum) means 'like a small saw', referring to the edges of the leaves.

[6] This species of Hypocalymma is found in low-lying areas at the base of low hills, often in Banksia woodland and with Eucalyptus todtiana, from near Hill River to the south of Badgingarra National Park in the Geraldton Sandplains and Swan Coastal Plain bioregions of south-western Western Australia.

[2][4] Hypocalymma serrulatum is listed as "Priority Two" by the Government of Western Australia Department of Biodiversity, Conservation and Attractions,[2] meaning that it is poorly known and from one or a few locations.