Hydrocotyle serendipita A.J. Perkins sp. nov. is a rare species of fire ephemeral from the Albany area of southwest Western Australia. The newly discovered species shares the fire ephemeral life history trait with the recently described H. phoenix A.J. Perkins. Based on a suite of vegetative synapomorphies, these two species appear to be closely related. Marked differences in mericarp shape and surface morphology, assist to differentiate the two species. Photographic images of H. serendipita are provided, along with a distribution map and a list of diagnostic features to aid in identification.