The shallow water cumacean fauna of Australia is relatively well known, particularly from the southern coasts. However, recent investigations in the collections of the Australian Museum and Museum Victoria have yielded 12 new species and one new genus of diastylid cumaceans, most from continental shelf and slope depths of Australia; one new species in Museum Victoria is from Canadian waters. The new genus Austroleptostylis is described, and the species Leptostylis recalvastra Hale, 1945 is transferred to it, creating the new combination Austroleptostylis recalvastra (Hale, 1945). The new species Anchistylis halei n. sp., Diastylis kapalae n. sp., Diastylopsis incompta n. sp. (from Canada), Diastylopsis senta n. sp., Diastylopsis trisetosa n. sp., Dimorphostylis nordaustraliana n. sp., Dimorphostylis roccatagliatai n. sp., Dimorphostylis triplicata n. sp., Makrokylindrus eirmoacanthus n. sp., Paradiastylis berentsae n. sp., P. botanybayensis n. sp., and P. occidensaustralis n. sp. are described. Diastylopsis diaphanes Zimmer, 1913 is transferred to Litogynodiastylis Gerken, 2001, creating the new combination Litogynodiastylis diaphanes (Zimmer, 1913), and D. bosphorica Băcescu, 1982 is transferred to Diastyloides Sars, 1900, creating the new combination Diastyloides bosphorica (Băcescu, 1982). The adult male and ovigerous female of Austroleptostylis recalvastra n. comb. are described. Keys to all Australian diastylid species are provided, as are global keys to all species of Diastylopsis and Paradiastylis.