Two new hosts are recorded forDeretrema minutumManter, 1954 from freshwater habitats at Lake Ellesmere, Canterbury. These are the mysidTenagotnysis chiltoniTattersall, 1923 which acts as a second intermediate host and harbours the encysted metacercariae, and the smelt,Retropinna retropinna(Richardson, 1848), which contains adult worms. AdultD. minutumwere also found in the inangaGalaxias maculatusJenyns, 1842. A large proportion of metacercariae within the crustacean host exhibited progenesis which results in the production of numerous eggs. Ovigerous metacercariae were identical with adultD. minutumrecovered from the intestine of freshwater fishes from Lake Ellesmere. A description of the metacercaria is given.