Gastrointestinal parasites are a major problem for sheep graziers and anthelmintic resistance has been reported worldwide. Given that in experimental circumstances, sheep helminths are able to develop in rabbits and hares, and that hares are very mobile and sympatric with sheep in many regions of Australia, free-living lagomorphs were investigated regarding carriage of ovine nematode parasites under field conditions. We performed specific counts of the nematode parasites in the gastro-intestinal tracts of 88 rabbits and 110 hares to determine their possible role in the cross-transmission of ovine nematode parasites between farms. Our study revealed that ruminant worms are common in hares (prevalence 71%) and that they are occasionally found in rabbits (4%). Statistical analyses showed no significant effects of age and sex of leporids regarding the prevalence of worms. However, while the ruminant worm Trichostrongylus colubriformis occurred more frequently in hares, rabbits presented more lagomorphs-specific T. retortaeformis. The lagomorph worm Graphidium strigosum was found mostly in rabbit stomachs obtained from one farm in central western New South Wales. Detection of T. rugatus, a ruminant worm, is reported for the first time in lagomorphs, infecting four hares and one rabbit from the region of Adelaide, South Australia. The potential for cross-transmission between hares and sheep in the natural environment is much more prevalent than previously believed.