Porpoloma Singer is a genus of mushrooms distinguished by a tricholomatoid habit and amyloid spores. The genus is restricted to temperate regions of the southern hemisphere, with currently accepted species known from New Zealand and South America. Apart from P. penetrans (Cleland) Grgur., which most likely does not belong in Porpoloma but is suggested to be a species of Heimiomyces Singer, no species of Porpoloma have been described from Australia. However, molecular phylogenetic analyses indicate the presence of at least nine species in Australia. Here, we describe P. flavilamellatum from sporing body material from New South Wales. The species is also detected from sequences generated from soil samples collected in Queensland. Porpoloma flavilamellatum is distinguished macroscopically from some members of the genus by having yellow lamellae, and by other members of the genus that also have yellowish lamellae (P. amyloideum (G. Stev.) E. Horak, P. coyan Garrido, P. sejunctum Singer) by having darker yellow lamellae, lacking a membranous annulus or zone on the stipe, and being found in habitats with Myrtaceae Juss. rather than Nothofagaceae Kuprian. It is distinguished from all other members of the genus Porpoloma by its unique phylogenetic position.