Plastic pollution is pervasive globally, causing harm to the natural environment, particularly marine and freshwater ecosystems. Aquatic species, including fish, are at risk of microplastics exposure, with ingestion being well documented. However, despite substantial knowledge of microplastics in marine environments, there has been limited research focus on plastic contamination in freshwater environments. Moreover, the hydrology of freshwater ecosystems, including drought and flood, is especially influenced by extreme weather events. With predicted increases in occurrence and intensity of extreme weather events due to the changing climate, it is important to understand the influence of these events on plastic pollution. Although some research has assessed microplastic patterns in flood waters, little has been done to assess impact of plastic pollution on fish during extreme weather events. We investigated the presence of microplastics in the gastrointestinal tracts of golden perch (Macquaria ambigua), collected from the lower Murray River in the years before, during and immediately after a major flooding event in 2022/2023. We also assessed if there were differences in microplastic ingestion between the river channel and flood plain habitats. Overall, we found microplastics in more than half of the samples, and discuss spatial and temporal patterns in abundance along with exploring potential sources and pathways. Ultimately, understanding the patterns of microplastics presence throughout a major flood event will help determine the potential future impacts of plastic pollution in the context of increasing extreme weather events.