Branchial bopyrids were investigated from hermit crabs collected in Singapore in August 2000. Two male and female bopyrid pairs belonging to the genus Asymmetrione were found on Diogenes avarus Heller and described as A. sallyae. One pair of bopyrids from the branchial chamber of Clibanarius infraspinatus Hilgendorf represents a new species of Pseudione that is described as P. kensleyi. This is the first report of isopod parasites on hermit crabs from Singapore and represents the first records of bopyrids from these hermit crab hosts.