A new species of the genus Wareniconcha, W. mercenarioides, belonging to the chemosymbiotic bivalve subkimily Pliocardiinae (family Vesicomyidae), is described from a Pliocene methane-seep deposit at Liog-Liog on Leyte Island, Philippines. With a length of almost 12 cm, this species is significantly larger than the six extant species currently considered as belonging to Wareniconcha. In addition to being very large, W. mercenarioides is more inflated and has a considerably more rounded shell outline compared to the oval shells of other Wareniconcha species. This is the first fossil record of Wareniconcha. Considering the overall similarity of the Leyte seep fauna to species living at vents and seeps in the vicinity of southern Japan, we anticipate that similarly large, and closely related species, might still be extant in the Indo-West Pacific region.