David Lodge’s thorough documentation of the rusty crayfish invasion in north temperate lakes over the past few decades provides important insight into how invasion dynamics change over time. Invasive species are thought to initially dominate biological communities because they have fewer natural enemies than native species. Over long timescales, as enemies such as pathogens accumulate in an invasive species, the density and impacts of the invader should decline. This process has rarely been documented, since few invasions are investigated over long timescales. Rusty crayfish populations have recently declined in many north temperate lakes, but the cause of these declines is uncertain. We examined how pathogens affect rusty crayfish fecundity, mortality, behavior, and ecological impacts in Trout Lake, Wisconsin, using controlled mesocosm experiments and field data from 12 sites. Rusty crayfish abundance data in Trout Lake has been collected periodically since the early 1980s, and our field sampling was conducted from 2021 – 2023. During our study, there was an outbreak of a microsporidian pathogen (Nosema rusticus) in the invasive crayfish population and a substantial decline in rusty crayfish abundance. We found that this pathogen reduced rusty crayfish fecundity and survival and was more prevalent at high density sites. We also found that infected crayfish were more lethargic, and that infected individuals had reduced ecological impacts due to trait-mediated effects of the pathogen. Crayfish in Trout Lake were also often infected with trematode parasites (Microphallus sp.). Our previous work on trematodes indicates that these parasites do not cause direct mortality but are associated with an increase in crayfish boldness. Rusty crayfish infected with trematodes have greater ecological impacts because they spend less time hiding. Finally, we observed an increase in the abundance of native virile crayfish in Trout Lake. Virile crayfish were often infected with trematodes, but none were infected with N. rusticus. Overall, this research demonstrates that pathogens can substantially alter the impacts of invasive species by changing their behavior and abundance, and in some cases, this can promote the recovery of the native ecological community.