Platyoides costeri is a species of spider in the family Trochanteriidae. It is endemic to the Western Cape province of South Africa.
Platyoides costeri is known only from the Western Cape, where it has been recorded from elevations between 4 and 250 m above sea level. The species was originally described from Mossel Bay.
The species inhabits the Fynbos biome. Like other scorpion spiders, it is a free-living wanderer with a flattened body adapted for life in narrow crevices under bark or rocks.
Only females of Platyoides costeri are known to science, though males have been collected but remain undescribed.
The species is listed as Data Deficient for taxonomic reasons, as males remain unknown and the full species range requires further study. It is protected in the Robberg Nature Reserve.