Endocrine disrupting chemicals (EDCs) can alter key life history traits and biological processes in wild animals by mimicking the action of natural hormones. While considerable attention has focused on understanding the impact of anthropogenic EDCs introduced into the environment, naturally occurring chemical compounds that can emulate EDCs may also be harmful. Plant secondary metabolites are one such group of chemicals, and while they play a primary role in herbivory defence, they can also cause a range of impacts for non-target species when leached into freshwater environments. Existing research shows that these plant-derived compounds like polyphenols and tannins can reduce growth, compromise development, impair reproduction, and alter communication pathways for a range of freshwater taxa. The effects of plant secondary metabolites on animal behaviour are, however, generally unknown. Here, I explored the effects of eucalyptus leachate on the mating behaviour and reproductive potential of a native freshwater fish species. Murray River rainbowfish (Melanotaenia fluviatilis) were exposed to two concentrations of eucalyptus leachate (5mg/L ‘low’ or 15mg/L ‘high’) for five weeks in total. I conducted mating behaviour assays prior to exposure and following two weeks of exposure to leachate, and fish were allowed to spawn at the end of the five-week exposure period. While male courtship and total female association time were unaffected, I found that ‘high’ treatment females spent more time associating with males that courted more. This result indicates a reduced capacity in exposed females to distinguish between male courtship effort. Additionally, ‘high’ treatment females had a reduced propensity to spawn following five weeks of leachate exposure. Collectively, my findings show that acute exposure to eucalyptus leachate can trigger negative behavioural changes and reduced spawning capacity. In turn, they demonstrate the potential for naturally occurring chemicals to cause drastic shifts in reproduction under elevated levels of eucalyptus leachate.