<p>Cities are hotspots for biological invasions, but the mechanisms facilitating invasive species in urban areas remain unclear. Urbanization can lead to changes to characteristics (i.e. traits) that modulate the potential of invaders to spread and further invade (i.e. invasiveness), facilitating success. Such an effect is often estimated by comparing mean trait differences between urban and non-urban populations of the invader. However, this approach overlooks that the uneven distribution of urban infrastructure (e.g. parks, building density) creates a mosaic of habitats with different characteristics that provides opportunity for varying local trait responses. This within-city trait variation can be fundamental for the success of invasive species in cities. In this study, we assess whether urban landscape heterogeneity, estimated as % impervious area, can modulate invasiveness. We use Goldfish as a model and show that populations occurring within the same city express varying life-history traits, as a function of landscape heterogeneity. Specifically, we found that imperviousness has a non-linear relationship with reproductive investment that is mediated by size. In small Goldfish, reproductive investment is initially reduced at low imperviousness but then rebounds at higher imperviousness, enhancing invasiveness. Meanwhile, body condition shows a linear response being negatively related to imperviousness. These results suggest that different populations of urban invaders may represent invasion fronts with varying invasion risk, which would require distinct actions from managers. This also implies that imperviousness should be minimized to avoid inadvertently enhancing the invasiveness of non-native species. Acknowledging within-city trait variation is critical for advancing our understanding of invasion dynamics, promoting biodiversity, and achieving sustainability in cities.</p>