Nutria (Myocastor coypus) is an invasive, semi-aquatic rodent that recently re-emerged in California’s Central Valley, threatening ecologically vital wetland habitats. To understand invasion dynamics, we aimed to identify the source of contemporary California nutria, assess genetic structure, estimate kinship to infer colonization social dynamics, and identify dispersal corridors. We sampled contemporary California nutria (n = 267), six other invasive populations across North America (n = 40), and historical samples from California fur farms (n = 10). We sequenced the cytochrome-b locus and used RADSeq to discover 6,809 SNP loci. Consistent with recent invasion, we found a single cytochrome-b haplotype among contemporary California nutria, while historical samples had several haplotypes no longer present. Nuclear and mitochondrial data revealed contemporary California nutria have close genetic affiliation with Oregon and Washington populations. SNP-based estimates of kinship indicated closely related individuals occupy the northern and southern leading edges of the invasion, while more central areas displayed low kinship and minimal genetic structure. Landscape genetic analyses identified dispersal corridors facilitating southern range expansion. We provide the first assessment of genetic relationships among nutria invaded regions in the United States, including insights into landscape connectivity and colonization dynamics that will ultimately aid eradication strategies.