Identifying contamination patterns on dairy farms is critical to controlling the potential transfer of undesirable microorganisms into both the animal herd and raw milk. In the case of Listeria species, this is particularly important as L. monocytogenes can cause severe illness in both humans and the dairy herd; L. ivanovii causing infection in the dairy herd. This study monitored contamination routes of Listeria species across 7 dairy farms located throughout Victoria. This included identifying contamination patterns across farms, and the state, through sampling at locations such as water supplies, farmland pastures, animal feed, the dairy herds, as well as raw milk. Pulsed-Field Gel Electrophoresis (PFGE) was utilised to examine the molecular ecology of the Listeria population. A diverse population of Listeria species was identified, with L. innocua (n=19) isolated most frequently, followed by L. seeligeri (n=6) and L. ivanovii (n=4), while L. monocytogenes (n=1) and L. grayi (n=1) were least common. Population analysis identified multiple clones present in geographically diverse locations throughout the state. Aquatic niches were a significant feature of the isolate distribution across farms, with frequent contamination of environmental water reservoirs utilised by farms as a main water source. Isolate contamination could be tracked from these water reservoirs through to feed water for animals. Mobile genetic elements conferring resistance to heavy metals were identified, suggesting adaption to heavy metals in the environment may be a feature of the population; 16% of isolates showed high resistance to cadmium. Results suggest groundwater may be an important distribution chain for Listeria species throughout the state. This study provides evidence for harbourage sites and contamination routes of Listeria species in farm environments across Victoria, and identifies the environmental water supply as a key entry route for Listeria into the farm environment. This knowledge will help direct future control strategies to help minimise the potential spread of Listeria into the farm system, and ultimately into raw milk and the dairy food chain.