Individual variation assessments are essential to better understand population and community dynamics, and ecosystem functioning. Although researchers have long recognized this aspect only recently has evidence accumulated about the ecological importance of variation within species. The incorporation of individual variation provides a more complete description of the effects a species may have on ecosystems and this detailed ecological knowledge can be especially important in the context of biological invasions. In this study, we used an invasion gradient of the signal crayfish Pacifastacus leniusculus to assess possible intrapopulation differences in key biological traits and evaluate possible changes in ecological impacts. For this, we collect individuals from the core and front of an invasion gradient to characterize several biological traits such as abundance, size, sex-ratio, physiological condition, personality, and trophic niche. In addition, we perform two laboratory experiments to assess possible differences regarding the consumption of prey, leaf mass loss, and nutrient cycling. Crayfish from the invasion front are predominantly male and display lower abundance. However, they are larger, exhibit superior physiological condition, demonstrate increased boldness and aggression, and have elevated nitrogen values. In addition, crayfish from the front consume more prey and more leafs and increase the concentration of nitrates and phosphates. Overall, the signal crayfish has different biological traits and has distinct ecological impacts along the invasion gradient. This study demonstrates the importance of assessing biological traits and impacts of invasive species at the intrapopulation level. Such an approach could improve and refine impact assessments with potential pay-offs in the development of more effective conservation and management strategies.